Fix a few windows file locking issues in env_chromium_unittests.

One just caused the temp dir to not be cleaned up. The other caused the test
to fail.

NOTRY=true
(These tests aren't run on the bots)

Review URL: https://codereview.chromium.org/33683002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@229966 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 229966