rbd: destroy header_oloc in rbd_dev_release()

Purely cosmetic at this point, as rbd doesn't use RADOS namespaces and
hence rbd_dev->header_oloc->pool_ns is always NULL.
Signed-off-by: NIlya Dryomov <idryomov@gmail.com>

drivers/block/rbd.c

@@ -3950,6 +3950,7 @@ static void rbd_dev_release(struct device *dev)
 	bool need_put = !!rbd_dev->opts;
 
 	ceph_oid_destroy(&rbd_dev->header_oid);
+	ceph_oloc_destroy(&rbd_dev->header_oloc);
 
 	rbd_put_client(rbd_dev->rbd_client);
 	rbd_spec_put(rbd_dev->spec);