Fixed #12876 -- Corrected a problem with recursive relations under deepcopy....

Fixed #12876 -- Corrected a problem with recursive relations under deepcopy. Thanks to elachuni for the patch.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@12700 bcc190cf-cafb-0310-a4f2-bffc1f526a37