res_rtp_asterisk: Raise event when RTP port is allocated

This change raises a testsuite event to provide what port
Asterisk has actually allocated for RTP. This ensures that
testsuite tests can remove any assumption of ports and instead
use the actual port in use.

ASTERISK-28070

Change-Id: I91bd45782e84284e01c89acf4b2da352e14ae044

res/res_rtp_asterisk.c

@@ -3492,6 +3492,7 @@ static int rtp_allocate_transport(struct ast_rtp_instance *instance, struct ast_
 		if (!ast_bind(rtp->s, &rtp->bind_address)) {
 			ast_debug(1, "Allocated port %d for RTP instance '%p'\n", x, instance);
 			ast_rtp_instance_set_local_address(instance, &rtp->bind_address);
+			ast_test_suite_event_notify("RTP_PORT_ALLOCATED", "Port: %d", x);
 			break;
 		}