bsc: cosmetic: T_guard timeout: add 'self.stop'

If the T_guard runs out, unless we self.stop, we might run into this
potentially confusing follow-up error:

00:23:04.206712 mtc BSC_Tests.ttcn:322 Dynamic test case error: Copying an unbound value of type @RSL_Types.RSL_Message.
00:23:04.206778 mtc BSC_Tests.ttcn:322 setverdict(error): fail -> error

Change-Id: I1d373159483bdd9f74e8944e430913e73c289e03
diff --git a/bsc/BSC_Tests.ttcn b/bsc/BSC_Tests.ttcn
index dc266ab..d8ca374 100644
--- a/bsc/BSC_Tests.ttcn
+++ b/bsc/BSC_Tests.ttcn
@@ -224,7 +224,10 @@
 /* global altstep for global guard timer; also takes care of responding RESET witH RESET-ACK */
 altstep as_Tguard() runs on test_CT {
 	var BSSAP_N_UNITDATA_ind ud_ind;
-	[] T_guard.timeout { setverdict(fail, "Timeout of T_guard"); }
+	[] T_guard.timeout {
+			setverdict(fail, "Timeout of T_guard");
+			self.stop;
+		}
 	/* always respond with RESET ACK to RESET */
 	[] BSSAP.receive(tr_BSSAP_UNITDATA_ind(?, ?, tr_BSSMAP_Reset)) -> value ud_ind {
 		BSSAP.send(ts_BSSAP_UNITDATA_req(ud_ind.callingAddress, ud_ind.calledAddress,