lib/DIAMETER: Allow sending CEA with AuthAppId

The new message is to be used by Gy interface emulation, which according
to RFC4006 uses AppId 4 "Credit Control Application". The application
is apparently not 3GPP vendor specific.

Change-Id: I0e33673d65140aad34d2efcae3c7f49154ceb99f
diff --git a/pgw/PGW_Tests.ttcn b/pgw/PGW_Tests.ttcn
index 34090d2..d9f4979 100644
--- a/pgw/PGW_Tests.ttcn
+++ b/pgw/PGW_Tests.ttcn
@@ -126,6 +126,7 @@
 		local_sctp_port := mp_pcrf_local_port,
 		origin_host := "pcrf.localdomain",
 		origin_realm := "localdomain",
+		auth_app_id := omit,
 		vendor_app_id := c_DIAMETER_3GPP_Gx_AID
 	};
 	vc_DIAMETER := DIAMETER_Emulation_CT.create(id);