fix bogus path_put() of nd->root after some unlazy_walk() failures

Failure to grab reference to parent dentry should go through the
same cleanup as nd->seq mismatch.  As it is, we might end up with
caller thinking it needs to path_put() nd->root, with obvious
nasty results once we'd hit that bug enough times to drive the
refcount of root dentry all the way to zero...
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

fs/namei.c

@@ -513,8 +513,7 @@ static int unlazy_walk(struct nameidata *nd, struct dentry *dentry)
 
 	if (!lockref_get_not_dead(&parent->d_lockref)) {
 		nd->path.dentry = NULL;	
-		rcu_read_unlock();
-		return -ECHILD;
+		goto out;
 	}
 
 	/*