[1.0.X] Applying a limit to a queryset that already had an upper limit of 0

wasn't working properly.

Backport of r9201 from trunk.


git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.0.X@9204 bcc190cf-cafb-0310-a4f2-bffc1f526a37