Fix messed up tests for dropout (#22893)
Summary:
Fix https://github.com/pytorch/pytorch/issues/22109.
I've confirmed with suo that this wasn't intentional.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/22893
Differential Revision: D16288640
Pulled By: Chillee
fbshipit-source-id: 00fd6fe418ecefb304866a723051d0e5451ba4d5
