Move unwrap logic from c10 to caffe2 (#21620)
Summary:
After https://github.com/pytorch/pytorch/pull/17072, we are allowed to pass Variables into ATen ops, thus there is no need to unwrap input variables in the c10 call path.
Note that since Caffe2 still expects inputs to be pure Tensors, we moved the unwrapping logic to the Caffe2 wrapper.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/21620
Differential Revision: D15763560
Pulled By: yf225
fbshipit-source-id: 5375f0e51eb320f380ae599ebf98e6b259f0bff8
