Fix for ConfBridge config parser unlocking channel mutex too many times

When looking up a ConfBridge profile, the config parser would, if it
found a channel datastore on the channel requesting the bridge profile,
unlock the channel mutex twice.  Since that's a little aggressive,
it now only unlocks it once.

(closes issue ASTERISK-19042)
Reported by: Matt Jordan
Tested by: Matt Jordan
Patches: 
  19042 uploaded by David Vossel (license 5628)
........

Merged revisions 349619 from http://svn.asterisk.org/svn/asterisk/branches/10


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@349634 65c4cc65-6c06-0410-ace0-fbb531ad65f3