Stop tests after failures

Call mtc.stop after setverdict(fail), add reasons to most failures and
fail with verdict error for internal errors.

Change-Id: I9b618235939fa41160b9be6677b121963d3ec857
diff --git a/sip/SIP_Tests.ttcn b/sip/SIP_Tests.ttcn
index f690dc7..24b3622 100644
--- a/sip/SIP_Tests.ttcn
+++ b/sip/SIP_Tests.ttcn
@@ -131,7 +131,7 @@
 private altstep as_Tguard() runs on ConnHdlr {
 	[] g_Tguard.timeout {
 		setverdict(fail, "Tguard timeout");
-		self.stop;
+		mtc.stop;
 	}
 }