Fix TCPStore wait() hang when key is previously set (#53860)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/53860
Fixes [#53840](https://github.com/pytorch/pytorch/issues/53840)
Right now [TCPStore wait([LIST_OF_KEYS_TO_AWAIT])](https://pytorch.org/docs/master/distributed.html#torch.distributed.Store.wait) will hang if any of the keys in [LIST_OF_KEYS_TO_AWAIT] has been previously set. This change will ensure that wait() is only waiting for the keys that have not been set
Before change:
```
# Case 1: HANG
store.set("1", "1")
store.wait(["1", "2"])
store.set("2", "2")
# Case 2: SUCCEED
store.wait(["1", "2"])
store.set("1", "1")
store.set("2", "2")
```
After change:
Both cases work
TODO: working on adding a test for wait()
Test Plan: Imported from OSS
Reviewed By: albanD
Differential Revision: D26999929
Pulled By: H-Huang
fbshipit-source-id: 8931749923c98b520366538f785af82ef37cca8e
