Move the final layer_preprocess in the encoder and decoder in to the variable scopes so that they don't share parameters.
Move the final layer_preprocess in the encoder and decoder in to the variable scopes so that they don't share parameters.

PiperOrigin-RevId: 169147528

vthorsteinsson/tensor2tensor,tensorflow/tensor2tensor,rsepassi/tensor2tensor,rsepassi/tensor2tensor,tensorflow/tensor2tensor,waterblue13/tensor2tensor,waterblue13/tensor2tensor,vthorsteinsson/tensor2tensor,rsepassi/tensor2tensor,tensorflow/tensor2tensor,tensorflow/tensor2tensor,rsepassi/tensor2tensor,vthorsteinsson/tensor2tensor,waterblue13/tensor2tensor,vthorsteinsson/tensor2tensor,tensorflow/tensor2tensor