Add python excepiton handling catch block to resolve deadlock (#35283)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/35283
https://github.com/pytorch/pytorch/issues/34260
Deadlock on destructing py::error_already_set.
There are request callback impls in Python, where Python exceptions could be thrown. For releasing Python exception py::objects, GIL must be held.
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_torchscript_functions_not_supported
```
Differential Revision: D7753253
fbshipit-source-id: 4bfaaaf027e4254f5e3fedaca80228c8b4282e39
