override protobuf serializer copy method

[fengzanfeng]

Because the [copy] method in parent class throw KryoException forever, this is very inefficient for protobuf message.

[CLAassistant]

Thank you for your submission, we really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.

---

Zanfeng Feng seems not to be a GitHub user. You need a GitHub account to be able to sign the CLA. If you have already a GitHub account, please add the email address used for this commit to your account.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[johnynek]

thanks! if you sign the CLA I will merge.

[fengzanfeng]

@johnynek I have signed the CLA for twitter/chill, thanks.

[johnynek]

huh, the bot things you have not. Can you click on the details link next to the yellow dot in the checks section?

[fengzanfeng]

I have done as you suggested. Is it ok now? @johnynek

[johnynek]

@decause can you give any help here? It seems like the CLA bot is not working correctly.

[fengzanfeng]

@decause could you giving help?

[decause]

I checked our list and can confirm that @fengzanfeng has signed the CLA as of 6/20/2018, even though it's not showing up here for some reason.

Go ahead an merge manually for now @johnynek and I'll follow-up with upstream to see what the issue is with the checks.

🚢

[decause]

submitted here: cla-assistant/cla-assistant#352