DIAMETER_Emulation: Notify user of CapabilityExchange

During start of the test case, we must wait until the IUT has
established a DIAMETER/SCTP connection to the testsuite.  Implement
this by means of a message on the DIAMETER_UNIT port and an associated
helper function.

Change-Id: I95434307efc67025ee6d373561f6d22398f959c5
diff --git a/mme/MME_Tests.ttcn b/mme/MME_Tests.ttcn
index 0516809..f9bcf6d 100644
--- a/mme/MME_Tests.ttcn
+++ b/mme/MME_Tests.ttcn
@@ -229,6 +229,8 @@
 	connect(vc_DIAMETER:DIAMETER_UNIT, self:DIAMETER_UNIT);
 	connect(vc_DIAMETER:DIAMETER_PROC, self:DIAMETER_PROC);
 	vc_DIAMETER.start(DIAMETER_Emulation.main(ops, pars, id));
+
+	f_diameter_wait_capability(DIAMETER_UNIT);
 }
 
 friend template (value) TAI ts_enb_S1AP_TAI(EnbParams enb) := {