mme: Fix seq_nr=0 being used everytime in Tx SGSNContextReq

Change-Id: I9a1a2dbceb4c4f30a8408c6f58bf645656e900bc
diff --git a/mme/MME_Tests.ttcn b/mme/MME_Tests.ttcn
index 50b89b3..2194e8a 100644
--- a/mme/MME_Tests.ttcn
+++ b/mme/MME_Tests.ttcn
@@ -890,6 +890,7 @@
 	var OCT3 ptmsi_sig;
 	var Gtp1cUnitdata gtpc_pdu;
 	var OCT4 old_mme_local_teid;
+	var  uint16_t gtpc_seq_nr := f_rnd_int(65535);
 
 	/* Derive NAS Token (and post-increment ul_count): */
 	var OCT32 nas_token := f_s1apem_derive_nas_token(g_pars.ue_pars.kasme);
@@ -899,7 +900,7 @@
 
 	SGSNContextReqPDU := ts_SGSNContextReqPDU(rai, new_sgsn_local_teid, f_inet_addr(mp_gn_local_ip),
 						  ptmsi := ts_PTMSI(ptmsi), ptmsi_sig := ts_PTMSI_sig(ptmsi_sig));
-	GTP.send(ts_GTPC_SGSNContextReq(g_gn_iface_peer, 0, SGSNContextReqPDU));
+	GTP.send(ts_GTPC_SGSNContextReq(g_gn_iface_peer, gtpc_seq_nr, SGSNContextReqPDU));
 
 	timer T := 5.0;
 	T.start;