SGSN_Tests: Wait for RAU Accept after receiving SecurityModeCmd

We don't want to pass the test or return from this function before
receiving a RAU accept. With Iu we expect a Security Mode
Command/Complete before the routing area is updated, but we do want to
wait for the actual RAU Accept or fail when receiving a RAU Reject.

Change-Id: Id89e2c6dae8cbdb5e8dee1c92960dc3346590a95
Related: OS#3727
diff --git a/sgsn/SGSN_Tests.ttcn b/sgsn/SGSN_Tests.ttcn
index 800c978..eb1fff2 100644
--- a/sgsn/SGSN_Tests.ttcn
+++ b/sgsn/SGSN_Tests.ttcn
@@ -2409,6 +2409,7 @@
 			var IntegrityProtectionAlgorithm uia_chosen := 0; /* 0 = standard_UMTS_integrity_algorithm_UIA1 */
 			BSSAP.send(ts_RANAP_SecurityModeComplete(uia_chosen));
 			BSSAP.receive(tr_RANAP_CommonId(imsi_hex2oct(g_pars.imsi)))
+			repeat;
 		}
 	[is_gb(ran_index)] BSSGP[ran_index].receive { repeat; }
 	[is_iu(ran_index)] BSSAP.receive { repeat; }