migration/colo.c: Add missed filter notify for Xen COLO.

We need to notify net filter to do checkpoint for Xen COLO, like KVM side.

Signed-off-by: Zhang Chen <chen.zhang@intel.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>

migration/colo.c

@@ -259,6 +259,8 @@ ReplicationStatus *qmp_query_xen_replication_status(Error **errp)
 void qmp_xen_colo_do_checkpoint(Error **errp)
 {
     replication_do_checkpoint_all(errp);
+    /* Notify all filters of all NIC to do checkpoint */
+    colo_notify_filters_event(COLO_EVENT_CHECKPOINT, errp);
 }
 #endif