Fixed #17898: Ensure create_superuser honors the 'db' argument from...

Fixed #17898: Ensure create_superuser honors the 'db' argument from post_sync_db. Thanks to charettes for the patch.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@17738 bcc190cf-cafb-0310-a4f2-bffc1f526a37