Fixed #11891 -- Ensured that attributes of get_absolute_url are preserved...

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

git-svn-id: http://code.djangoproject.com/svn/django/trunk@12766 bcc190cf-cafb-0310-a4f2-bffc1f526a37