[1.1.X] Fixed #11891 -- Ensured that attributes of get_absolute_url are...

[1.1.X] Fixed #11891 -- Ensured that attributes of get_absolute_url are preserved through the metaclass. Thanks to nfg for the report and patch.

Backport of r12766 from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.1.X@12767 bcc190cf-cafb-0310-a4f2-bffc1f526a37