NS_Emulation: Handle NS_PROV_LINK_STATUS_DOWN

This happens e.g. if FrameRelay detects a "service affecting condition",
i.e. the link is considered dead.

Change-Id: I7409079f5e2b77cc08ccc93d1b0baa72720cefb8
diff --git a/library/NS_Emulation.ttcnpp b/library/NS_Emulation.ttcnpp
index dc8e0ec..ec3386f 100644
--- a/library/NS_Emulation.ttcnpp
+++ b/library/NS_Emulation.ttcnpp
@@ -612,6 +612,13 @@
 		var PDU_NS rf;
 		var ASP_Event evt;
 
+		[] NSCP.receive(NS_Provider_Evt:{link_status:=NS_PROV_LINK_STATUS_DOWN}) {
+			log("Provider Link went down");
+			Tns_test.stop;
+			Tns_alive.stop;
+			f_change_state(NSVC_S_DEAD_BLOCKED);
+		}
+
 		[] NS_SP.receive(NsCtrlRequest:DisableReq) {
 			/* To make NS-VCG remove us from list of active NS-VC */
 			f_change_state(NSVC_S_DEAD_BLOCKED);