Fix a couple random test failures.
Review Request #7950 — Created Feb. 7, 2016 and submitted
These have been broken for a while due to an issue during cleanup with the temp
directory not being empty. This change switches fromrmdirtormtree.
Ran unit tests.
Tool: Pyflakes Processed Files: reviewboard/scmtools/cvs.py Tool: PEP8 Style Checker Processed Files: reviewboard/scmtools/cvs.py