MGCP_Test: fix TC_one_crcx_loopback_rtp_implicit

The testcase TC_one_crcx_loopback_rtp_implicit uses
f_TC_one_crcx_loopback_rtp, which creates the RTP flow with IPv4
addresses but since we do not send a local RTP IP address with the CRCX
to the MGW, the MGW will prefer IPv6, which means that we get an IPv6
address back while the RTP strem is IPv4 on the TTCN3 side.

Related: OS#5123
Change-Id: I80498737d5b32f28b62e0c17cce1969b54af948c
diff --git a/mgw/MGCP_Test.ttcn b/mgw/MGCP_Test.ttcn
index c4f97a8..5575f7a 100644
--- a/mgw/MGCP_Test.ttcn
+++ b/mgw/MGCP_Test.ttcn
@@ -1693,14 +1693,14 @@
 
 	/* Create one connection in loopback mode, test if the RTP packets are
 	 * actually reflected */
-	function f_TC_one_crcx_loopback_rtp(boolean one_phase := true) runs on dummy_CT {
+	function f_TC_one_crcx_loopback_rtp(charstring local_ip, charstring remote_ip, boolean one_phase := true) runs on dummy_CT {
 		var RtpFlowData flow;
 		var MgcpEndpoint ep := c_mgw_ep_rtpbridge & "1@" & c_mgw_domain;
 		var MgcpCallId call_id := '1225'H;
 		var RtpemStats stats;
 
 		f_init(ep);
-		flow := valueof(t_RtpFlow(mp_local_ipv4, mp_remote_ipv4, 111, "GSM-HR-08/8000/1"));
+		flow := valueof(t_RtpFlow(local_ip, remote_ip, 111, "GSM-HR-08/8000/1"));
 		flow.em.portnr := 10000;
 		f_flow_create(RTPEM[0], ep, call_id, "loopback", flow, one_phase := one_phase);
 
@@ -1725,7 +1725,7 @@
 	/* Create one connection in loopback mode, test if the RTP packets are
 	 * actually reflected */
 	testcase TC_one_crcx_loopback_rtp() runs on dummy_CT {
-		 f_TC_one_crcx_loopback_rtp(one_phase := true)
+		 f_TC_one_crcx_loopback_rtp(mp_local_ipv4, mp_remote_ipv4, one_phase := true)
 	}
 
 	/* Same as above, but we will intenionally not tell the MGW where to
@@ -1733,7 +1733,7 @@
 	 * loopback mode, so the MGW should take the originating address from
 	 * the incoming RTP packet and send it back to the source */
 	testcase TC_one_crcx_loopback_rtp_implicit() runs on dummy_CT {
-		 f_TC_one_crcx_loopback_rtp(one_phase := false)
+		 f_TC_one_crcx_loopback_rtp(mp_local_ipv6, mp_remote_ipv6, one_phase := false)
 	}