message: Updates AsyncCheckpointSaverHook so it does save a checkpoint when the global step is zero.
  This is the behavior of the synchronous checkpoint saver, so I think it's what users expect.
diff: @@ -148,10 +148,6 @@ class AsyncCheckpointSaverHook(basic_session_run_hooks.CheckpointSaverHook):
  def _save(self, session, step, asynchronous=True):
  """Saves the latest checkpoint, returns should_stop."""
  - # Skip saving on step 0
  - if step == 0:
  - return
  -
  def _save_fn():
  """Run the saver process."""
  logging.info("Saving checkpoints for %d into %s.", step, self._save_path)
  