test cleanup: skipped test TestV3AuthOldRevConcurrent

[endocrimes]

TestV3AuthOldRevConcurrent is currently blanket skipped and the referenced issue #10408 was closed by the stalebot rather than a person or commit.

With the context from here: #10468 (comment) I think it might've been replaced with the retry interceptor here: https://github.com/etcd-io/etcd/blob/main/client/v3/retry_interceptor.go#L156-L165.

The test passes when removing the skip, which implies the behaviour was fixed (potentially by the interceptor). But I'm not really sure and would like to get deeper understanding before fixing/removing it.

cc @jingyih @mitake

[mitake]

@endocrimes Thanks for sharing it, I’ll check it.

[mitake]

@endocrimes I think it's fine to re-enable the test, thanks a lot for figuring this out. I opened #13828 could you review?