Fix multi-gpu training (fixes #1088)
Fix multi-gpu training (fixes #1088)

Summary: Pull Request resolved: https://github.com/pytorch/fairseq/pull/1089

Differential Revision: D17108918

Pulled By: myleott

fbshipit-source-id: 818c77a5bbf3b146028991aca64d79b93f144b28

pytorch/fairseq,pytorch/fairseq,pytorch/fairseq