message: Make TensorBoard callback V1 only run on chief in multi-worker setting.
diff: @@ -158,6 +158,10 @@ class TensorBoard(callbacks.Callback):
  # One profiler session is running if it is True.
  self._is_profiling = False
  + # TensorBoard should only write summaries on the chief when in a
  + # Multi-Worker setting.
  + self._chief_worker_only = True
  +
  def _init_writer(self, model):
  """Sets file writer."""
  if context.executing_eagerly():
  