Make RRef leak detection always print a warning log (#31922)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/31922
For better debugging, `test_rref_leak` failure in https://app.circleci.com/jobs/github/pytorch/pytorch/4135881, as per discussion in https://github.com/pytorch/pytorch/pull/31888.
ghstack-source-id: 96375261
Test Plan:
# Unit tests
```
buck test mode/dev-nosan //caffe2/test:rpc_fork
buck-out/gen/caffe2/test/rpc_fork\#binary.par -r test_wait_all_workers
buck-out/gen/caffe2/test/rpc_fork\#binary.par -r test_rref_leak
```
# Stress runs
```
buck test mode/dev-nosan //caffe2/test:rpc_fork_thrift -- test_stress_light_rpc --stress-runs 10
```
```
buck test mode/dev-nosan //caffe2/test:rpc_spawn_thrift -- test_stress_light_rpc --stress-runs 10
```
```
buck test mode/dev-nosan //caffe2/test:rpc_fork_thrift -- test_stress_heavy_rpc --stress-runs 10
```
```
buck test mode/dev-nosan //caffe2/test:rpc_spawn_thrift -- test_stress_heavy_rpc --stress-runs 10
```
Differential Revision: D19302814
fbshipit-source-id: 51632aede98e01689f8bc0f266788a9b020daa15
