VFS: pass correct vnode to fs calls in default get_vnode_name

The opendir and closedir/free_dircookie hooks were called with
mismatched vnode. It seems only googlefs is actually affected by this,
since all other fs without a get_vnode_name just don't are about the
passed vnode arg to closedir and free_dircookie.

Now I should really get some sleep!

src/system/kernel/fs/vfs.cpp

@@ -2528,8 +2528,8 @@ get_vnode_name(struct vnode* vnode, struct vnode* parent, struct dirent* buffer,
 			}
 		}
 
-		FS_CALL(vnode, close_dir, cookie);
-		FS_CALL(vnode, free_dir_cookie, cookie);
+		FS_CALL(parent, close_dir, cookie);
+		FS_CALL(parent, free_dir_cookie, cookie);
 	}
 	return status;
 }