OSS tracing compliant transformer to unbreak master (#1299)

Summary:
Pull Request resolved: https://github.com/pytorch/fairseq/pull/1299

 LevT calls into tracing compliant transformer we didn't plan to OSS earlier. This is a workaround to unbreak the master. Will revisit and simplify the code later.

Reviewed By: pipibjc

Differential Revision: D18110339

fbshipit-source-id: 3bb51c56c2c20f45db1d5786d030b374b412eab1

fairseq/models/levenshtein_transformer.py

@@ -16,7 +16,7 @@ import torch
 import torch.nn as nn
 import torch.nn.functional as F
 from fairseq.models import register_model, register_model_architecture
-from fairseq.models.fb_tracing_transformer import (
+from fairseq.models.tracing_compliant_transformer import (
     TracingTransformerDecoder,
     TracingTransformerEncoder,
     TracingTransformerModel,