allow forward hooks in tracing (#23613)
Summary:
As far as I could tell forward hooks work out of the box, so allow them in the tracing. We don't have any way of supporting backward hooks though.
Fixes https://github.com/pytorch/pytorch/issues/20862 and fixes https://github.com/pytorch/pytorch/issues/17571
Pull Request resolved: https://github.com/pytorch/pytorch/pull/23613
Differential Revision: D16601437
Pulled By: eellison
fbshipit-source-id: ecf5dc6201ca08b3b9afdb9fcdb0fda8741133a9
