epdg: Fix instance in CreateSession Re S2b-U PGW F-TEID IE

According to 3GPP TS 29.274 Table 7.2.2-1, instance=1.

Change-Id: If0e2425e0a64e528990bfd589b858d0955a4677a
diff --git a/epdg/EPDG_Tests.ttcn b/epdg/EPDG_Tests.ttcn
index 03ea275..a7c9509 100644
--- a/epdg/EPDG_Tests.ttcn
+++ b/epdg/EPDG_Tests.ttcn
@@ -448,7 +448,7 @@
 		/* Upon rx of CreateSession, emulate PGW asking the AAA server. */
 		f_S6b_AA_success();
 
-		fteid_c_ie := ts_GTP2C_FTEID(FTEID_IF_S2b_ePDG_GTPC, g_pars.teic_local, 0,
+		fteid_c_ie := ts_GTP2C_FTEID(FTEID_IF_S2b_ePDG_GTPC, g_pars.teic_local, 1,
 					f_inet_addr(mp_s2b_local_ip), omit);
 		fteid_u_ie := ts_GTP2C_FTEID(FTEID_IF_S2bU_ePDG_GTPU, g_pars.bearer.teid_local, 4,
 					f_inet_addr(mp_s2b_local_ip), omit);