Ensure frames are only freed once.

(closes issue #16361)
 Reported by: vlad
 Patches: 
       20100208__issue16361.diff.txt uploaded by tilghman (license 14)
 Tested by: kenny, bloodoff, misaksen


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@245729 65c4cc65-6c06-0410-ace0-fbb531ad65f3