test: fix logic of retry in health check

[Yiyiyimu]

Signed-off-by: yiyiyimu [email protected]

So when error is not due to etcd disconnection (has no healthy etcd endpoint available), it could correctly return error rather than just continue

[Yiyiyimu]

cc @spacewander

[b03jsj]

I found that problem too, I do it by myself. I also found grpc token is invalid err