Base setting but quicker with only 2 epochs.

def rlmb_ppo_quick():
  """Base setting but quicker with only 2 epochs."""
  hparams = rlmb_ppo_base()
  hparams.epochs = 2
  hparams.model_train_steps = 25000
  hparams.ppo_epochs_num = 700
  hparams.ppo_epoch_length = 50
  return hparams