With asyncio, we must close the writer half of a pair
Also rework the get_next_msg to work better.
Still need to allow stop_following to interrupt get_next_msg
Since we are rebasing to at least Python 3.6, and with
some extra ctypes wranging of the ssl context, we can likely
remove PyOpenSSL. Take first steps by removing it from 'sockapi'.
Have confluent executable become the 'top level' for eventlet, to allow
work on 'de-eventleting' on 'main.py'.
Rework tlvdata to deal with either a socket or a reader, writer tuple.
Using TLS with asyncio is easiest with the 'open_connection'
semantics, which force either a Protocol handler (callback based) or
dual streams. While protocol approach ends with a more socket-like
'transport', the 'protocol' half is a bit unwieldy. So reader and writer
streams instead.
The two files should be identical. confluentsrv.py exists
only because PyInstaller struggles unless the target is a
'py' file and does not have some namespace conflict with a
module.
