Fixed #10833 -- Corrected load_backend so that it actually loads the requested...

Fixed #10833 -- Corrected load_backend so that it actually loads the requested backend, rather than always loading settings.DATABASE_BACKEND. Thanks to Alex Gaynor for the report and fix.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@10560 bcc190cf-cafb-0310-a4f2-bffc1f526a37