mgw: Allow setting udp ip/port with wildcard osmux in f_flow_create_osmux()

This will be needed once IPv4+IPv6 support is used, since we want to set
the remote IP addr in CRCX for convinience to get an IP adr from ther
same family during CRCX, while still allowing for testing Osmux CID
wildcard value.

Change-Id: I3abd80b1c0053004aab3d03e09fada1129a59765
diff --git a/mgw/MGCP_Test.ttcn b/mgw/MGCP_Test.ttcn
index 24bfdaf..deb9f3e 100644
--- a/mgw/MGCP_Test.ttcn
+++ b/mgw/MGCP_Test.ttcn
@@ -417,10 +417,13 @@
 			 * part that tells the MGW where we are listening for Osmux streams
 			 * that come from the MGW. We get a fully working connection in
 			 * one go. */
-			rx_hdl := c_OsmuxemDefaultRxHandle;
-			rx_hdl.cid := flow.osmux_cid;
-			f_osmuxem_register_rxhandle(pt, rx_hdl);
-			flow.osmux_cid_sent := true;
+			if (flow.osmux_cid != -1) {
+				/* We may still want to negotiate osmux CID later at MDCX */
+				rx_hdl := c_OsmuxemDefaultRxHandle;
+				rx_hdl.cid := flow.osmux_cid;
+				f_osmuxem_register_rxhandle(pt, rx_hdl);
+				flow.osmux_cid_sent := true;
+			}
 			cmd := ts_CRCX_osmux(get_next_trans_id(), ep, mode, call_id, flow.osmux_cid);
 			cmd.sdp := ts_SDP(flow.em.hostname, flow.em.hostname, "23", "42",
 					  flow.em.portnr, { int2str(flow.pt) }, attributes);