[RPC] [Minor] RPC entry point cleanup (#34292)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/34292
This is to finish a cleanup request from https://github.com/pytorch/pytorch/pull/34733#discussion_r392479110.
ghstack-source-id: 104361618
Test Plan:
```
buck test mode/dev-nosan //caffe2/test/distributed/rpc/jit:rpc_fork
buck build mode/dev-nosan //caffe2/test/distributed/rpc/jit:rpc_fork && \
buck-out/gen/caffe2/test/distributed/rpc/jit/rpc_fork\#binary.par \
-r test_return_local_script_class_rref_in_py_and_use_in_script
buck build mode/dev-nosan //caffe2/test/distributed/rpc/jit:rpc_fork && \
buck-out/gen/caffe2/test/distributed/rpc/jit/rpc_fork\#binary.par \
-r test_return_local_script_module_rref_in_py_and_use_in_script
```
Differential Revision: D7436759
fbshipit-source-id: b509c47fb612ec3486ff1199c005eba69480ee05
