libceph: init event->node in ceph_osdc_create_event()

The red-black node node in the ceph osd event structure is not
initialized in create_osdc_create_event().  Because this node can
be the subject of a RB_EMPTY_NODE() call later on, we should ensure
the node is initialized properly for that.
Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Sage Weil <sage@inktank.com>

net/ceph/osd_client.c

@@ -1563,6 +1563,7 @@ int ceph_osdc_create_event(struct ceph_osd_client *osdc,
 	event->data = data;
 	event->osdc = osdc;
 	INIT_LIST_HEAD(&event->osd_node);
+	RB_CLEAR_NODE(&event->node);
 	kref_init(&event->kref);   /* one ref for us */
 	kref_get(&event->kref);    /* one ref for the caller */
 	init_completion(&event->completion);