[1.2.X] Fixed a few more cases of the tests not properly restoring sys.path...

[1.2.X] Fixed a few more cases of the tests not properly restoring sys.path (follow up on [14430]).  Backport of [14431].

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.2.X@14432 bcc190cf-cafb-0310-a4f2-bffc1f526a37