[1.0.X] Fixed #9023 -- Corrected a problem where cached attribute values would...

[1.0.X] Fixed #9023 -- Corrected a problem where cached attribute values would cause a delete to cascade to a related object even when the relationship had been set to None. Thanks to TheShark for the report and test case, and to juriejan and Jacob for their work on the patch.

Merge of r11009 from trunk.


git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.0.X@11010 bcc190cf-cafb-0310-a4f2-bffc1f526a37