gsm48: Release the LU procedure only after the TMSI REALL_COMPL

We send a LU Accept with the TMSI as the MI. According to the
spec the phone should store this new TMSI and send a TMSI
REALLOCATION COMPLETE to us. We will release the LU then and this
should trigger the release procedure.
diff --git a/openbsc/src/gsm_04_08.c b/openbsc/src/gsm_04_08.c
index 5eb6a24..c3bf64f 100644
--- a/openbsc/src/gsm_04_08.c
+++ b/openbsc/src/gsm_04_08.c
@@ -282,8 +282,11 @@
 			subscr_update(conn->subscr, conn->bts,
 				      GSM_SUBSCRIBER_UPDATE_ATTACHED);
 
-			/* try to close channel ASAP */
-			release_loc_updating_req(conn);
+			/*
+			 * The gsm0408_loc_upd_acc sends a MI with the TMSI. The
+			 * MS needs to respond with a TMSI REALLOCATION COMPLETE
+			 * (even if the TMSI is the same).
+			 */
 			break;
 
 		default:
@@ -969,6 +972,7 @@
 		       conn->subscr ?
 				subscr_name(conn->subscr) :
 				"unknown subscriber");
+		release_loc_updating_req(conn);
 		break;
 	case GSM48_MT_MM_IMSI_DETACH_IND:
 		rc = gsm48_rx_mm_imsi_detach_ind(msg);