MGCP_Test: do not use module parameter mp_test_ip (statsd)

The module parameter mp_test_ip was added with the following commit:
Change-Id I61e23e264bc85eb36d07431c7839fb445c110947

There is already mp_local_ipv4, which has the same function, so we
should remove mp_test_ip again and use mp_local_ipv4 to set up the
receiving of statsd information.

Change-Id: I70f33aed4102c67118cc6701c2578a70c0dfe604
Related: SYS#5535
diff --git a/mgw/MGCP_Test.ttcn b/mgw/MGCP_Test.ttcn
index 3aa7926..b0891f5 100644
--- a/mgw/MGCP_Test.ttcn
+++ b/mgw/MGCP_Test.ttcn
@@ -78,7 +78,6 @@
 		PortNumber mp_local_rtp_port_base := 10000;
 		PortNumber mp_local_osmux_port := 1985;
 		PortNumber mp_mgw_statsd_port := 8125;
-		charstring mp_test_ip := "127.0.0.1";
 	}
 
 	private function f_vty_enable_osmux(boolean osmux_on) runs on dummy_CT {
@@ -150,7 +149,7 @@
 				connect(vc_OsmuxEM:CTRL, self:OsmuxEM);
 			}
 
-			f_init_statsd("VirtCallAgent", vc_STATSD, mp_test_ip, mp_mgw_statsd_port);
+			f_init_statsd("VirtCallAgent", vc_STATSD, mp_local_ipv4, mp_mgw_statsd_port);
 			connect(self:STATSD_PROC, vc_STATSD:STATSD_PROC);
 
 			f_statsd_reset();