[1.1.X] Tweaked the model_formsets test to work around a weird sorting problem...

[1.1.X] Tweaked the model_formsets test to work around a weird sorting problem between versions of Postgres. Thanks to Alex Gaynor for the report.

Backport of r11953 from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.1.X@11954 bcc190cf-cafb-0310-a4f2-bffc1f526a37