stp: Time out after 5s if expected M3UA doesn't arrive

No need to wait for the global timeout here.

Change-Id: I279aacf2215ccd63a6e52c6a71cda3b500a3795c
diff --git a/stp/STP_Tests_M3UA.ttcn b/stp/STP_Tests_M3UA.ttcn
index b76d9be..1c25bae 100644
--- a/stp/STP_Tests_M3UA.ttcn
+++ b/stp/STP_Tests_M3UA.ttcn
@@ -90,6 +90,8 @@
 
 friend function f_M3UA_exp(integer idx, template (present) PDU_M3UA msg) runs on RAW_M3UA_CT {
 	var M3UA_RecvFrom rx;
+	timer T := 5.0;
+	T.start;
 	alt {
 	[] M3UA[idx].receive(t_M3UA_RecvFrom(msg)) {
 		setverdict(pass);
@@ -99,6 +101,10 @@
 			   "while waiting for ", msg);
 		mtc.stop;
 		}
+	[] T.timeout {
+		setverdict(fail, "Timeout waiting for M3UA[", idx, "] ", msg);
+		mtc.stop;
+		}
 	}
 }