res/res_rtp_asterisk: clear smoother when local bridging

p2p_write updates txformat but doesn't require a smoother.  If a smoother
was created by another bridge type the smoother could fall out of date causing
one way audio issues.  To prevent this the smoother is now destroyed on the
start of native bridge.

ASTERISK-28284 #close

Change-Id: I84e67f144963787fff9b4d79ac500514fb40cdc6

res/res_rtp_asterisk.c

@@ -7480,6 +7480,10 @@ static int ast_rtp_local_bridge(struct ast_rtp_instance *instance0, struct ast_r
 
 	ao2_lock(instance0);
 	ast_set_flag(rtp, FLAG_NEED_MARKER_BIT | FLAG_REQ_LOCAL_BRIDGE_BIT);
+	if (rtp->smoother) {
+		ast_smoother_free(rtp->smoother);
+		rtp->smoother = NULL;
+	}
 	ao2_unlock(instance0);
 
 	return 0;