Ensure that logmsgs are freed properly

Messages sent while the logger thread is shutting down will now have
their associated callid freed properly.
........

Merged revisions 382574 from http://svn.asterisk.org/svn/asterisk/branches/11


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@382575 65c4cc65-6c06-0410-ace0-fbb531ad65f3