Fixed #10622 -- Resolved an issue with model inheritence and list_editable....

Fixed #10622 -- Resolved an issue with model inheritence and list_editable. Thanks oyvind and Alex Gaynor.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@10178 bcc190cf-cafb-0310-a4f2-bffc1f526a37