[1.2.X] Fixed #11513 -- Ensure that the redirect at the end of an object...

[1.2.X] Fixed #11513 -- Ensure that the redirect at the end of an object change won't redirect to a page for which the user doesn't have permission. Thanks to rlaager for the report and draft patch, and to Julien Phalip for the final patch.

Backport of r15584 from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.2.X@15586 bcc190cf-cafb-0310-a4f2-bffc1f526a37