Fix an RTP instance reference count leak in chan_motif.

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

channels/chan_motif.c

@@ -426,10 +426,12 @@ static void jingle_session_destructor(void *obj)
 	}
 
 	if (session->rtp) {
+		ast_rtp_instance_stop(session->rtp);
 		ast_rtp_instance_destroy(session->rtp);
 	}
 
 	if (session->vrtp) {
+		ast_rtp_instance_stop(session->vrtp);
 		ast_rtp_instance_destroy(session->vrtp);
 	}