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/ggsn_tests/GGSN_Tests.ttcn b/ggsn_tests/GGSN_Tests.ttcn
index 7a7ff97..203dcbf 100644
--- a/ggsn_tests/GGSN_Tests.ttcn
+++ b/ggsn_tests/GGSN_Tests.ttcn
@@ -210,6 +210,7 @@
 			local_sctp_port := PCRF_PORT,
 			origin_host := "pcrf.localdomain",
 			origin_realm := "localdomain",
+			auth_app_id := omit,
 			vendor_app_id := c_DIAMETER_3GPP_Gx_AID
 		};
 		vc_Gx := DIAMETER_Emulation_CT.create(id);