BUG: positional getitem indexing with list on Series with duplicate integer index fails 
Create test case for issue GH17347

- [x] closes #17347 
- [x] tests added / passed
Hello @tranctan96! Thanks for updating this PR. We checked the lines you've touched for [PEP 8](https://www.python.org/dev/peps/pep-0008) issues, and found:



There are currently no PEP 8 issues detected in this Pull Request. Cheers! :beers: 

##### Comment last updated at 2019-04-15 17:04:32 UTC # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/26083?src=pr&el=h1) Report
> :exclamation: No coverage uploaded for pull request base (`master@190a69e`). [Click here to learn what that means](https://docs.codecov.io/docs/error-reference#section-missing-base-commit).
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/26083/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/26083?src=pr&el=tree)

```diff
@@            Coverage Diff            @@
##             master   #26083   +/-   ##
=========================================
  Coverage          ?   91.94%           
=========================================
  Files             ?      175           
  Lines             ?    52444           
  Branches          ?        0           
=========================================
  Hits              ?    48221           
  Misses            ?     4223           
  Partials          ?        0
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.5% <ø> (?)` | |
| #single | `40.75% <ø> (?)` | |


------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/26083?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/26083?src=pr&el=footer). Last update [190a69e...c0fe2e0](https://codecov.io/gh/pandas-dev/pandas/pull/26083?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/26083?src=pr&el=h1) Report
> :exclamation: No coverage uploaded for pull request base (`master@190a69e`). [Click here to learn what that means](https://docs.codecov.io/docs/error-reference#section-missing-base-commit).
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/26083/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/26083?src=pr&el=tree)

```diff
@@            Coverage Diff            @@
##             master   #26083   +/-   ##
=========================================
  Coverage          ?   91.95%           
=========================================
  Files             ?      175           
  Lines             ?    52412           
  Branches          ?        0           
=========================================
  Hits              ?    48195           
  Misses            ?     4217           
  Partials          ?        0
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.51% <ø> (?)` | |
| #single | `40.73% <ø> (?)` | |


------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/26083?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/26083?src=pr&el=footer). Last update [190a69e...d25af61](https://codecov.io/gh/pandas-dev/pandas/pull/26083?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 thanks @tranctan96 