NFSv4.x: Fix a refcount leak in nfs_callback_up_net

commit 98b0f80c upstream.

On error, the callers expect us to return without bumping
nn->cb_users[].
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

fs/nfs/callback.c

@@ -301,6 +301,7 @@ static int nfs_callback_up_net(int minorversion, struct svc_serv *serv, struct n
 err_socks:
 	svc_rpcb_cleanup(serv, net);
 err_bind:
+	nn->cb_users[minorversion]--;
 	dprintk("NFS: Couldn't create callback socket: err = %d; "
 			"net = %p\n", ret, net);
 	return ret;