Fix interaction between tracing and FusedLayerNorm (#1038)
Fix interaction between tracing and FusedLayerNorm (#1038)

Summary: Pull Request resolved: https://github.com/fairinternal/fairseq-py/pull/1038

Differential Revision: D20030410

Pulled By: myleott

fbshipit-source-id: c64a2ddfdd379a93359e87fd1a1226c7f19f1158

pytorch/fairseq,pytorch/fairseq,pytorch/fairseq