message: rafs/iostats: mark fop recorder as success if offset beyond file size
  As read() returns OK(0), we also mark recoder as success if it happens.
diff: @@ -539,6 +539,7 @@ impl FileSystem for Rafs {
  let mut recorder = FopRecorder::settle(Read, ino, &self.ios);
  let inode = self.sb.get_inode(ino, false)?;
  if offset >= inode.size() {
  + recorder.mark_success(0);
  return Ok(0);
  }
  let desc = inode.alloc_bio_desc(offset, size as usize)?;
  