Fixed #15560 -- Cleaned up some redundant post->put redirections in the...

Fixed #15560 -- Cleaned up some redundant post->put redirections in the class-based generic views. Thanks to maney for the report and patch.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@15763 bcc190cf-cafb-0310-a4f2-bffc1f526a37