Fixed #5631 -- When fieldsets contains a field that is on the same line, it is...

Fixed #5631 -- When fieldsets contains a field that is on the same line, it is now collapsable when collapse is set in classes. Thanks andybak for some research and Karen Tracey for the patch.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@8177 bcc190cf-cafb-0310-a4f2-bffc1f526a37