[1.2.X] Fixed #14250 - FileBasedCacheTests.test_cull test failure

  
This patch makes the cull behaviour (which files deleted and how many
deleted) deterministic.

Backport of [13705] from trunk.


git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.2.X@13706 bcc190cf-cafb-0310-a4f2-bffc1f526a37