[1.2.X] Fixed #14975, #14925 -- Added some cache flushing to avoid some...

[1.2.X] Fixed #14975, #14925 -- Added some cache flushing to avoid some cross-test effects. Thanks to jsdalton and rpbarlow for the reports.

Backport of r15192 from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.2.X@15193 bcc190cf-cafb-0310-a4f2-bffc1f526a37