adjusting trainer_model_based for different modes in atari envs.
adjusting trainer_model_based for different modes in atari envs.

PiperOrigin-RevId: 209502286

tensorflow/tensor2tensor,vthorsteinsson/tensor2tensor,tensorflow/tensor2tensor,vthorsteinsson/tensor2tensor,tensorflow/tensor2tensor,vthorsteinsson/tensor2tensor,tensorflow/tensor2tensor,vthorsteinsson/tensor2tensor,tensorflow/tensor2tensor