message: daemon: Turn on the xattr feature of passthrough_fs
  The filesystem of overlayfs upperdir needs to support xattr.
  Passthrough_fs supports xattr but not enabled by nydusd daemon. This
  commit enables it.
diff: @@ -421,6 +421,7 @@ fn fs_backend_factory(cmd: &FsBackendMountCmd) -> DaemonResult<BackFileSystem> {
  do_import: false,
  writeback: true,
  no_open: true,
  + xattr: true,
  ..Default::default()
  };
  // TODO: Passthrough Fs needs to enlarge rlimit against host. We can exploit `MountCmd`
  