rtp_stream: sanely cancel MGW endpoint FSM notify

libosmo-mgcp-client recently introduced osmo_mgcpc_ep_cancel_notify() to cancel
notification if a notify target FSM deallocates. Use it for sanity in
rtp_stream FSM cleanup, the notify target for endpoint FSMs.

Depends: I41687d7f3a808587ab7f7520f46dcc3c29cff92d (osmo-mgw)
	 I14f7a46031327fb2b2047b998eae6ad0bb7324ad (osmo-mgw)
Change-Id: I351bb8e8fbc46eb629bcd599f6453e2c84c15015
diff --git a/src/libmsc/rtp_stream.c b/src/libmsc/rtp_stream.c
index c3880bf..d78743e 100644
--- a/src/libmsc/rtp_stream.c
+++ b/src/libmsc/rtp_stream.c
@@ -220,6 +220,7 @@
 {
 	struct rtp_stream *rtps = fi->priv;
 	if (rtps->ci) {
+		osmo_mgcpc_ep_cancel_notify(osmo_mgcpc_ep_ci_ep(rtps->ci), fi);
 		osmo_mgcpc_ep_ci_dlcx(rtps->ci);
 		rtps->ci = NULL;
 	}