message: filecache: stop setting AsyncRequestState::Cancelled on stopping
  Temporary workadround.
  Otherwise, the rest prefetch requests will be dropped directly.
diff: @@ -254,8 +254,8 @@ impl BlobCache for FileCacheEntry {
  }
  fn stop_prefetch(&self) -> StorageResult<()> {
  - self.prefetch_state
  - .store(AsyncRequestState::Cancelled as u32, Ordering::Release);
  + // self.prefetch_state
  + // .store(AsyncRequestState::Cancelled as u32, Ordering::Release);
  self.workers.stop();
  Ok(())
  }
  