message: Account for old run config, more robust num trainers
diff: @@ -448,9 +448,7 @@ class TensorForestEstimator(estimator.Estimator):
  """
  # Override default number of trainers if config is provided.
  if num_trainers == 1 and config is not None:
  - num_trainers = config.num_worker_replicas
  - if trainer_id == 0 and config is not None:
  - trainer_id = config.global_id_in_cluster
  + num_trainers = max(1, config.num_worker_replicas)
  super(TensorForestEstimator, self).__init__(
  model_fn=get_model_fn(
  @@ -572,9 +570,7 @@ class MultiForestMultiHeadEstimator(estimator.Estimator):
  model_fns = []
  # Override default number of trainers if config is provided.
  if num_trainers == 1 and config is not None:
  - num_trainers = config.num_worker_replicas
  - if trainer_id == 0 and config is not None:
  - trainer_id = config.global_id_in_cluster
  + num_trainers = max(1, config.num_worker_replicas)
  for i in range(len(params_list)):
  params = params_list[i].fill()
  @@ -723,7 +719,7 @@ class CoreTensorForestEstimator(core_estimator.Estimator):
  """
  # Override default number of trainers if config is provided.
  if num_trainers == 1 and config is not None:
  - num_trainers = config.num_worker_replicas
  + num_trainers = max(1, config.num_worker_replicas)
  if trainer_id == 0 and config is not None:
  trainer_id = config.global_id_in_cluster
  