[1.2.X] Refs #15550 -- Corrected another primary-key ordering problem in the...

[1.2.X] Refs #15550 -- Corrected another primary-key ordering problem in the modelforms tests. Thanks to bberes for the report.

Backport of r15753 from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.2.X@15754 bcc190cf-cafb-0310-a4f2-bffc1f526a37