Print more self-explanatory error message on bind/connect failures

When sockets cannot be bound or connected, the existing TTCN-3 code prints
the following rather cryptic error messages:

"IPA-CTRL-IPA(47)@f70ff1fd5cfd: Dynamic test case error: Using the value of an optional field containing omit. (Transport endpoint is not connected)"

The "Transport endpoint is not connected" sort-of gives it away, but
let's make it more explicit by introducing explicit checks for the
res.connId and manual setverdict(fail) statements with proper error
message.

Change-Id: Id22a1b5189d81c4fca03d5e7aff60ffdd1ad56bf
diff --git a/bts/BTS_Tests.ttcn b/bts/BTS_Tests.ttcn
index 49bf45e..bc3f186 100644
--- a/bts/BTS_Tests.ttcn
+++ b/bts/BTS_Tests.ttcn
@@ -396,6 +396,10 @@
 	var Result res;
 	res := TRXC_CodecPort_CtrlFunct.f_IPL4_connect(BB_TRXC, mp_bb_trxc_ip, mp_bb_trxc_port,
 							"", -1, -1, {udp:={}}, {});
+	if (not ispresent(res.connId)) {
+		setverdict(fail, "Could not connect to trx-control interface of trxcon, check your configuration");
+		self.stop;
+	}
 	g_bb_trxc_conn_id := res.connId;
 }
 
@@ -1043,6 +1047,10 @@
 	var Result res;
 	res := TRXC_CodecPort_CtrlFunct.f_IPL4_connect(BB_TRXC, mp_bb_trxc_ip, mp_bb_trxc_port,
 							"", -1, -1, {udp:={}}, {});
+	if (not ispresent(res.connId)) {
+		setverdict(fail, "Could not connect to trx-control interface of trxcon, check your configuration");
+		self.stop;
+	}
 	g_bb_trxc_conn_id := res.connId;
 }