TST: Correct results with np.size and crosstab (#4003)
 - [x] closes #4003
 - [x] tests added / passed
 - [x] passes ``git diff upstream/master | flake8 --diff``


## [Current coverage](https://codecov.io/gh/pandas-dev/pandas/pull/14755?src=pr) is 85.26% (diff: 100%)


> No coverage report found for **master** at e991141.

> Powered by [Codecov](https://codecov.io?src=pr). Last update [e991141...e703a8d](https://codecov.io/gh/pandas-dev/pandas/compare/e991141f3c13117035fb2a08f4e64b4c18c9d5a9...e703a8d565ee550e5c8bf6e821eeb48cae17d890?src=pr) can you rebase Rebased and all green @jreback  thanks!