Fixed #15029 -- Moved to database backends the ability to decide if two DATABASES items are different when creating temporary databases for tests.
hG: Enter commit message.  Lines beginning with 'HG:' are removed.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@15392 bcc190cf-cafb-0310-a4f2-bffc1f526a37