Fix hub model loading
Fix hub model loading

Summary: Pull Request resolved: https://github.com/fairinternal/fairseq-py/pull/1012

Differential Revision: D19587452

Pulled By: myleott

fbshipit-source-id: f97e8140224059388093251cb38ba14c4a41af31

pytorch/fairseq,pytorch/fairseq,pytorch/fairseq