Fix a couple random test failures.
Fix a couple random test failures.

These have been broken for a while due to an issue during cleanup with the temp
directory not being empty. This change switches from `rmdir` to `rmtree`.

Testing done:
Ran unit tests.

Reviewed at https://reviews.reviewboard.org/r/7950/

reviewboard/reviewboard,reviewboard/reviewboard,sgallagher/reviewboard,davidt/reviewboard,chipx86/reviewboard,davidt/reviewboard,sgallagher/reviewboard,brennie/reviewboard,reviewboard/reviewboard,chipx86/reviewboard,davidt/reviewboard,reviewboard/reviewboard,chipx86/reviewboard,brennie/reviewboard,brennie/reviewboard,davidt/reviewboard,sgallagher/reviewboard,brennie/reviewboard,sgallagher/reviewboard,chipx86/reviewboard