[1.2.X] Ensured that the test suite creates the default DB before any others.

Refs #14799. Backport of [14756], and see the note there for a caveat.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.2.X@14757 bcc190cf-cafb-0310-a4f2-bffc1f526a37