IuPS: send Security Mode Command, track the new_key flag.

Change-Id: I0b2593c2df13b79eb36975b0d302e31cfdf8bb09
diff --git a/openbsc/src/gprs/gprs_sgsn.c b/openbsc/src/gprs/gprs_sgsn.c
index 19b0a1b..dd7e008 100644
--- a/openbsc/src/gprs/gprs_sgsn.c
+++ b/openbsc/src/gprs/gprs_sgsn.c
@@ -244,6 +244,7 @@
 
 	ctx->ran_type = MM_CTX_T_UTRAN_Iu;
 	ctx->iu.ue_ctx = uectx;
+	ctx->iu.new_key = 1;
 	ctx->mm_state = GMM_DEREGISTERED;
 	ctx->auth_triplet.key_seq = GSM_KEY_SEQ_INVAL;
 	ctx->ctrg = rate_ctr_group_alloc(ctx, &mmctx_ctrg_desc, 0);