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/selftest/Selftest.ttcn b/selftest/Selftest.ttcn
index 1ff17fe..826d244 100644
--- a/selftest/Selftest.ttcn
+++ b/selftest/Selftest.ttcn
@@ -55,6 +55,10 @@
 	var Result res;
 	map(self:IP, system:IP);
 	res := IPL4asp_PortType.f_IPL4_connect(IP, "127.0.0.1", 55555, "", -1,-1, {tcp:={}});
+	if (not ispresent(res.connId)) {
+		setverdict(fail, "Could not connect to TCP port, check your configuration");
+		self.stop;
+	}
 	g_ip_conn_id := res.connId;
 }