Fixed #12640 -- Corrected a regression in test suite construction order...

Fixed #12640 -- Corrected a regression in test suite construction order introduced by #12255. Also updated the docs to reflect what the test code has always done. Thanks to Ramiro Morales for the report and patch.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@12261 bcc190cf-cafb-0310-a4f2-bffc1f526a37