message: rafs: replace root inode's permission bits with 0o755
  This is majorly a workaround since the root directory is
  given permission bits of 0o750, ending up with preventing
  other users accessing the rootfs.
  So a image with user(not root) set can't be started.
diff: @@ -566,8 +566,16 @@ impl FileSystem for Rafs {
  _handle: Option<u64>,
  ) -> Result<(libc::stat64, Duration)> {
  let mut recorder = FopRecorder::settle(Getattr, ino, &self.ios);
  - let attr = self.get_inode_attr(ino).map(|r| {
  +
  + let attr = self.get_inode_attr(ino).map(|mut r| {
  recorder.mark_success(0);
  + // Only touch permissions bits. This trick is some sort of workaround
  + // since nydusify gives root directory permission of 0o750 and fuse mount
  + // options `rootmode=` does not affect root directory's permission bits, ending
  + // up with preventing other users from accessing the container rootfs.
  + if ino == ROOT_ID {
  + r.mode = r.mode & !0o777 | 0o755;
  + }
  r
  })?;
  Ok((attr.into(), self.sb.meta.attr_timeout))
  