hybrid vsock lost the first package when it was just created

[teawater]

We meet the issue with firecracker in kata-containers/kata-containers#79.
And I found that hybrid vsock will drop or truncate the first package and qemu doesn't have this issue.
I add code that send an empty package and wait the first package arrive from client to handle this issue in https://github.com/alipay/grpc/commit/811660d28e3771a162cd5ece0d1e950168476ac8.

[sandreim]

Thanks for logging this @teawater. We will look into it and update you.

[sandreim]

@teawater We need more context into the problem as our integration tests pass without requiring the workaround that you implemented. Can you please provide steps and some more information on the setup that reproduces this issue ? Ideally that would be the most simple scenario that triggers the bug.

[teawater]

@sandreim Thanks for your comments.
I found that this is an issue of kata. I just post a PR to fix this issue in kata-containers/agent#696