ceph: after an MDS request, do callback and completions

No MDS requests use r_callback today, but that will change in the
future. The OSD client always does r_callback and then completes
r_completion. Let's have the MDS client do the same.
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: "Yan, Zheng" <zyan@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

fs/ceph/mds_client.c

@@ -2384,8 +2384,7 @@ static void complete_request(struct ceph_mds_client *mdsc,
 {
 	if (req->r_callback)
 		req->r_callback(mdsc, req);
-	else
-		complete_all(&req->r_completion);
+	complete_all(&req->r_completion);
 }
 
 /*