Replace calls of Type::_th_tensor. (#14877)

Replace calls of Type::_th_tensor. (#14877)

Summary:
_th_tensor is moving off Type, so these calls need to be replaced.

Unfortunately, replacing these with a full-fledged solution [e.g. from_storage(..., TensorOptions)] is a bit complicated because the storage itself fully defines the Type (modulo variable).  It's simpler to just wait for the Variable/Tensor merge rather than to solve this now, so instead I changed the call sites to: at::empty({0}, type.options()).set_(storage...).

This isn't great because we are also trying to get rid of Type::options, but this seems to be the lesser-of-two-evils.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/14877

Differential Revision: D13374310

Pulled By: gchanan

fbshipit-source-id: eb953ed041507e6190d6f32e383912e5a08311cd