Update Async to server library

[hueifeng]

Modify some methods to be asynchronous.

[shirhatti]

Solves #12334

[halter73]

This at least partially solves #12334. There are more places we call Complete() outside of an async context which will likely be trickier to fix.

[hueifeng]

@halter73 I have modified some of the others. I am not sure whether we should keep both synchronous and asynchronous methods. I found that Abort is a synchronous method, and I am not sure whether to change it to asynchronous?

[halter73]

@hueifeng Thanks for working on this issues. I made my last comment about there being other calls to Complete() just so we don't prematurely close #12334. I wasn't asking you to address everything. I was going to merge your PR as it was.

It looks like you're on the right track though. If it gets too messy, I might just take the initial commit.

@halter73 I have modified some of the others. I am not sure whether we should keep both synchronous and asynchronous methods. I found that Abort is a synchronous method, and I am not sure whether to change it to asynchronous?

For internal interfaces and types, it's OK to get rid of the synchronous methods if they're not called.

[pranavkm]

Bad rebase?