epdg: expect AAA_server tx SAR against HSS upon AA on s6B interface

The AAA-Server informs the HSS when the session is created at the PGW.

Change-Id: I1b81f1a2225f54d0f8f679e53d87f342feb495be
diff --git a/epdg/EPDG_Tests.ttcn b/epdg/EPDG_Tests.ttcn
index 0e9cbed..de5e7a8 100644
--- a/epdg/EPDG_Tests.ttcn
+++ b/epdg/EPDG_Tests.ttcn
@@ -392,6 +392,10 @@
 	S6b.send(ts_DIA_S6b_AAR(g_pars.imsi,
 				int2oct(DIA_TS29_373_MIP6_Feature_Vector_GTPv2_SUPPORTED, 8),
 				g_pars.apn, hbh_id := hbh_id, ete_id := ete_id));
+
+	/* AAR in S6b in AAA-Server triggers Service-Assignment Request/Answer towards HSS: */
+	as_DIA_SWx_SA_success();
+
 	alt {
 	[] S6b.receive(tr_DIA_S6b_AAA) -> value rx_dia {}
 	[] S6b.receive(PDU_DIAMETER:?) -> value rx_dia {