[abis] Dispatch a IPAC restart ACK/NACK signal

* Add the NACK version to the list
* Dispatch the signal when we receive the message
* Handle it in ipaccess-config by exiting the application
diff --git a/openbsc/src/ipaccess/ipaccess-config.c b/openbsc/src/ipaccess/ipaccess-config.c
index 29b9a9b..432179e 100644
--- a/openbsc/src/ipaccess/ipaccess-config.c
+++ b/openbsc/src/ipaccess/ipaccess-config.c
@@ -202,6 +202,14 @@
 		return ipacc_msg_ack(ipacc_data->msg_type, ipacc_data->bts);
 	case S_NM_TEST_REP:
 		return test_rep(signal_data);
+	case S_NM_IPACC_RESTART_ACK:
+		printf("The BTS has acked the restart. Exiting.\n");
+		exit(0);
+		break;
+	case S_NM_IPACC_RESTART_NACK:
+		printf("The BTS has nacked the restart. Exiting.\n");
+		exit(0);
+		break;
 	default:
 		break;
 	}