Call old slow decoding when fetching logits.
Call old slow decoding when fetching logits.

PiperOrigin-RevId: 170281924

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