Fix memory leaks

(closes issue ASTERISK-22368)
Reported by: Corey Farrell
Patches:
     issueA22368_mixmonitor_free_filename.patch uploaded by wdoekes (license 5674)
........

Merged revisions 398004 from http://svn.asterisk.org/svn/asterisk/branches/10


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/11@398011 65c4cc65-6c06-0410-ace0-fbb531ad65f3