When setting up an RTP instance the RTCP portion of the instance
keeps a reference to the instance itself. In order to release this
reference and stop RTCP the stop API call must be called before
destroying the instance.
(closes issue ASTERISK-20751)
Reported by: joshoa
git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/11@377021 65c4cc65-6c06-0410-ace0-fbb531ad65f3