Change handling of DataParallel in ONNX exporter (#23365)
Summary:
Don't automatically unwrap top layer DataParalllel for users. Instead, we provide useful error information and tell users what action to take.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/23365
Reviewed By: zrphercule
Differential Revision: D16514273
Pulled By: houseroad
fbshipit-source-id: f552de5c53fb44807e9d9ad62126c98873ed106e
