Fixed #10976 -- Isolated contrib.auth tests so they will always pass,...

Fixed #10976 -- Isolated contrib.auth tests so they will always pass, regardless of any local templates. Thanks to aarond10 for the report, and SmileyChris for turning that into a patch.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@12420 bcc190cf-cafb-0310-a4f2-bffc1f526a37