Avoid unnecessary refcount bump in unary operators. (#20331)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/20331
ghimport-source-id: 26588acca171555182714c6b6f89610564e228a1
Differential Revision: D15295193
Pulled By: ezyang
fbshipit-source-id: 44b7a8b4c9d41003a6559be2af0bd4f0ada54b31
