fixes for exporter issue of bi-transformer model (#597)
fixes for exporter issue of bi-transformer model (#597)

Summary:
Pull Request resolved: https://github.com/pytorch/fairseq/pull/597

Pull Request resolved: https://github.com/facebookresearch/pytext/pull/424

Fixes two issues:
1. the new Layernorm has issues in exporting
2. fix tensorboard writing by using the "RAW" operator_export_type

Differential Revision: D14610694

fbshipit-source-id: 1b859f54c571a90766128ab28539a9901375c3e6

pytorch/fairseq,pytorch/fairseq,pytorch/fairseq