Preserve module hierarchy on traced modules (#15101)
Summary:
We need this, for example, to properly call `_unpack` when we have a traced module in the hierarchy
Pull Request resolved: https://github.com/pytorch/pytorch/pull/15101
Differential Revision: D13468467
Pulled By: jamesr66a
fbshipit-source-id: c2b6740b12cde6e23395d12e42d4fc2c4c7ca3f2
