ceph: add missing spin_unlock at ceph_mdsc_build_path()

one of the paths was missing spin_unlock
Signed-off-by: Yehuda Sadeh <yehuda@hq.newdream.net>

fs/ceph/mds_client.c

@@ -1495,6 +1495,7 @@ char *ceph_mdsc_build_path(struct dentry *dentry, int *plen, u64 *base,
 			     pos, temp);
 		} else if (stop_on_nosnap && inode &&
 			   ceph_snap(inode) == CEPH_NOSNAP) {
+			spin_unlock(&temp->d_lock);
 			break;
 		} else {
 			pos -= temp->d_name.len;