[rpc][easy] move unnecessary python call directly to pybind (#33174)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/33174
Closes https://github.com/pytorch/pytorch/issues/32780. It looks like
this is the only callsite where we do `_get_current_rpc_agent().foo()`, and we
can do this directly in the pybind layer to save some overhead.
ghstack-source-id: 98200664
Test Plan: All UTs should pass.
Differential Revision: D19828786
fbshipit-source-id: 5c34a96b5a970e57e6a1fdf7f6e54c1f6b88f3d8
