Port THNN to ATen/Parallel (#20032)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/20032
ghimport-source-id: f8e1a4c7726585f2d1c894b64e3687ede6177282
Differential Revision: D15247960
Pulled By: ilia-cher
fbshipit-source-id: de784c0002cbe074c87f912a5824e8a75683dbf8
