Add a dummy first_batch to EpochBatchIterating
Add a dummy first_batch to EpochBatchIterating

Summary: Add a dummy first_batch to EpochBatchIterating

Reviewed By: myleott

Differential Revision: D25337800

fbshipit-source-id: c387c4c39533c161cb160a84ad4f99e71c66f73e

pytorch/fairseq,pytorch/fairseq,pytorch/fairseq