CI: fix db usage in CI
closes #24528
reverts behavior in #24485 
canonical way to run tests is ``test_fast.sh`` (or can also specify ``-m 'not single'`` (or ``--skip-db``)
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24529?src=pr&el=h1) Report
> Merging [#24529](https://codecov.io/gh/pandas-dev/pandas/pull/24529?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/b9284a2cd87fc305106fd75836dc96d7e00a0210?src=pr&el=desc) will **increase** coverage by `10.93%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/24529/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/24529?src=pr&el=tree)

```diff
@@             Coverage Diff             @@
##           master   #24529       +/-   ##
===========================================
+ Coverage   31.88%   42.81%   +10.93%     
===========================================
  Files         166      166               
  Lines       52427    52427               
===========================================
+ Hits        16714    22445     +5731     
+ Misses      35713    29982     -5731
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `?` | |
| #single | `42.81% <ø> (+10.93%)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/24529?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/indexes/accessors.py](https://codecov.io/gh/pandas-dev/pandas/pull/24529/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9hY2Nlc3NvcnMucHk=) | `54% <0%> (-10%)` | :arrow_down: |
| [pandas/core/internals/concat.py](https://codecov.io/gh/pandas-dev/pandas/pull/24529/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW50ZXJuYWxzL2NvbmNhdC5weQ==) | `60.07% <0%> (-7.12%)` | :arrow_down: |
| [pandas/core/nanops.py](https://codecov.io/gh/pandas-dev/pandas/pull/24529/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvbmFub3BzLnB5) | `32.07% <0%> (+0.37%)` | :arrow_up: |
| [pandas/core/arrays/period.py](https://codecov.io/gh/pandas-dev/pandas/pull/24529/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL3BlcmlvZC5weQ==) | `41.54% <0%> (+0.93%)` | :arrow_up: |
| [pandas/core/dtypes/missing.py](https://codecov.io/gh/pandas-dev/pandas/pull/24529/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZHR5cGVzL21pc3NpbmcucHk=) | `58.52% <0%> (+1.13%)` | :arrow_up: |
| [pandas/core/arrays/base.py](https://codecov.io/gh/pandas-dev/pandas/pull/24529/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL2Jhc2UucHk=) | `57.05% <0%> (+1.17%)` | :arrow_up: |
| [pandas/io/formats/csvs.py](https://codecov.io/gh/pandas-dev/pandas/pull/24529/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2Zvcm1hdHMvY3N2cy5weQ==) | `68.63% <0%> (+1.18%)` | :arrow_up: |
| [pandas/core/arrays/timedeltas.py](https://codecov.io/gh/pandas-dev/pandas/pull/24529/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL3RpbWVkZWx0YXMucHk=) | `40% <0%> (+1.23%)` | :arrow_up: |
| [pandas/tseries/offsets.py](https://codecov.io/gh/pandas-dev/pandas/pull/24529/diff?src=pr&el=tree#diff-cGFuZGFzL3RzZXJpZXMvb2Zmc2V0cy5weQ==) | `45.63% <0%> (+1.35%)` | :arrow_up: |
| [pandas/compat/\_\_init\_\_.py](https://codecov.io/gh/pandas-dev/pandas/pull/24529/diff?src=pr&el=tree#diff-cGFuZGFzL2NvbXBhdC9fX2luaXRfXy5weQ==) | `49.8% <0%> (+1.54%)` | :arrow_up: |
| ... and [63 more](https://codecov.io/gh/pandas-dev/pandas/pull/24529/diff?src=pr&el=tree-more) | |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24529?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24529?src=pr&el=footer). Last update [b9284a2...b30cfdb](https://codecov.io/gh/pandas-dev/pandas/pull/24529?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24529?src=pr&el=h1) Report
> Merging [#24529](https://codecov.io/gh/pandas-dev/pandas/pull/24529?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/b9284a2cd87fc305106fd75836dc96d7e00a0210?src=pr&el=desc) will **increase** coverage by `60.43%`.
> The diff coverage is `0%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/24529/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/24529?src=pr&el=tree)

```diff
@@             Coverage Diff             @@
##           master   #24529       +/-   ##
===========================================
+ Coverage   31.88%   92.31%   +60.43%     
===========================================
  Files         166      166               
  Lines       52427    52427               
===========================================
+ Hits        16714    48398    +31684     
+ Misses      35713     4029    -31684
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.73% <0%> (+60.45%)` | :arrow_up: |
| #single | `43.01% <0%> (+11.13%)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/24529?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/util/\_tester.py](https://codecov.io/gh/pandas-dev/pandas/pull/24529/diff?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvX3Rlc3Rlci5weQ==) | `23.8% <0%> (ø)` | :arrow_up: |
| [pandas/util/\_test\_decorators.py](https://codecov.io/gh/pandas-dev/pandas/pull/24529/diff?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvX3Rlc3RfZGVjb3JhdG9ycy5weQ==) | `90.54% <0%> (+4.05%)` | :arrow_up: |
| [pandas/compat/\_\_init\_\_.py](https://codecov.io/gh/pandas-dev/pandas/pull/24529/diff?src=pr&el=tree#diff-cGFuZGFzL2NvbXBhdC9fX2luaXRfXy5weQ==) | `57.91% <0%> (+9.65%)` | :arrow_up: |
| [pandas/core/config\_init.py](https://codecov.io/gh/pandas-dev/pandas/pull/24529/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvY29uZmlnX2luaXQucHk=) | `99.24% <0%> (+9.84%)` | :arrow_up: |
| [pandas/core/reshape/util.py](https://codecov.io/gh/pandas-dev/pandas/pull/24529/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvcmVzaGFwZS91dGlsLnB5) | `100% <0%> (+11.53%)` | :arrow_up: |
| [pandas/core/api.py](https://codecov.io/gh/pandas-dev/pandas/pull/24529/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXBpLnB5) | `100% <0%> (+13.33%)` | :arrow_up: |
| [pandas/compat/numpy/\_\_init\_\_.py](https://codecov.io/gh/pandas-dev/pandas/pull/24529/diff?src=pr&el=tree#diff-cGFuZGFzL2NvbXBhdC9udW1weS9fX2luaXRfXy5weQ==) | `92.85% <0%> (+14.28%)` | :arrow_up: |
| [pandas/io/formats/console.py](https://codecov.io/gh/pandas-dev/pandas/pull/24529/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2Zvcm1hdHMvY29uc29sZS5weQ==) | `74.24% <0%> (+16.66%)` | :arrow_up: |
| [pandas/core/dtypes/inference.py](https://codecov.io/gh/pandas-dev/pandas/pull/24529/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZHR5cGVzL2luZmVyZW5jZS5weQ==) | `98.46% <0%> (+18.46%)` | :arrow_up: |
| [pandas/plotting/\_compat.py](https://codecov.io/gh/pandas-dev/pandas/pull/24529/diff?src=pr&el=tree#diff-cGFuZGFzL3Bsb3R0aW5nL19jb21wYXQucHk=) | `87.5% <0%> (+18.75%)` | :arrow_up: |
| ... and [126 more](https://codecov.io/gh/pandas-dev/pandas/pull/24529/diff?src=pr&el=tree-more) | |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24529?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24529?src=pr&el=footer). Last update [b9284a2...24e5d6b](https://codecov.io/gh/pandas-dev/pandas/pull/24529?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 thanks @datapythonista i think this is good now. @datapythonista so welcome to simplify this, but in a followup.