Use GIL to guard decref of jit::toPyObj return value in processRpc (#38376)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/38376
Test Plan: Imported from OSS
Differential Revision: D21540179
Pulled By: mrshenli
fbshipit-source-id: 082fa5f11da7fc1f083710b498e72abc5ba2c244
