Move implementation of an attended-transfer-complete sound from one channel

driver into a common place for multiple channel drivers.
(closes issue #13152)
 Reported by: caio1982
 Patches: 
       atxfer_complete_sound3.diff uploaded by caio1982 (license 22)


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@134401 65c4cc65-6c06-0410-ace0-fbb531ad65f3