pytorch

16959153 - Make _wait_all_workers() support being called for multiple times (#32624)

Make _wait_all_workers() support being called for multiple times (#32624) Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/32624 We need this PR to resolve the issue mentioned in https://github.com/pytorch/pytorch/issues/31325#issuecomment-574918917. The solution is for each `_wait_all_workers()` call, there is a sequence ID added, to identify different calls. ghstack-source-id: 97277591 Test Plan: ``` buck test mode/dev-nosan //caffe2/test/distributed/rpc:rpc_fork -- test_wait_all_workers buck build mode/dev-nosan //caffe2/test/distributed/rpc:rpc_fork buck-out/gen/caffe2/test/distributed/rpc/rpc_fork\#binary.par -r test_wait_all_workers ``` Differential Revision: D5739520 fbshipit-source-id: a64131e09c365179624700514422f5375afe803f