[1.1.X] Fixed #13509 -- Modified the comment tests so that signal cleanup...

[1.1.X] Fixed #13509 -- Modified the comment tests so that signal cleanup doesn't rely on garbage collection. Thanks to Alex Gaynor for the report and patch.

Backport of r13204 from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.1.X@13206 bcc190cf-cafb-0310-a4f2-bffc1f526a37