Asyncio and fork() does not mix

[kristjanvalur]

The asyncio ConnectionPool contains a lot of code, inherited from the synchronous part, which tries to play safe with sockets after a fork() call.

However, python asyncio and fork does not play well together at all:
python/cpython#66197

Basically, one should never fork a process with a running event loop. As such, the code comparing PIDs is not helping with anything for async.

I propose that these rudiments be removed from the async code for clarity and simplicity.