don't try to set training after ScriptModule has been initialized. (#23680)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/23680
Now when initializing a ScriptModule during the torch.jit.load()
process, there is already a cpp module backing the thing. That means
that setting training will overwrite whatever the initialized
ScriptModule had.
This PR splits apart the common "set up internal state" part of the
Module __init__ and calls that from ScriptModule.__init__ and
Module.__init__, leaving the "nn.Module-specific" part (setting
`self.training`) for the nn.Module __init__
Test Plan: Imported from OSS
Differential Revision: D16606959
Pulled By: suo
fbshipit-source-id: f7ea6b36551ff4e4472b7685f65731d5cfab87fd