[1.0.X] Fixed #11134: signals recievers that disconnect during their...

[1.0.X] Fixed #11134: signals recievers that disconnect during their processing no longer mess things up for other handlers. Thanks, Honza Kral. Backport of [10831] from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.0.X@10832 bcc190cf-cafb-0310-a4f2-bffc1f526a37