respect grad guard for torch.jit._fork and torch.jit._wait (#16101)
Summary:
respect grad guard for torch.jit._fork and torch.jit._wait.
Verified that the test failed without the fix, and pass with the fix.
Ideally I would like to enable and disable grad inside the forked function.
It doesn't seems like it's supported at this moment. This code handles that
as well.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/16101
Differential Revision: D13708374
Pulled By: gqchen
fbshipit-source-id: 0533f080c4d0253fb4c61d2a0d3cc22de5721a09
