'-' to 'infection-monkey-relay-control-message: -'

…enger

Add get_potential_users and remove pipe handling

Integrate TCPConnectionHandler and RelayUserHandler into TCPRelay
Remove TCPProxy

If there's an uncaught error in the thread, the error won't propagate to the caller and we wouldn't know what went wrong from the logs. This fixes things and all uncaught errors get logged

If we were unsuccessful in starting the pipe, we don't want to sit
around and wait for a relay user to connect.

sock.recv takes two parameters instead of one

run() blocks, start() starts the run method on a different thread.

When a socket is closed, select.select() returns the socket in the
read_list. A closed socket can be detected by attempting to read from
it. If 0 data is read, then the socket is closed.

See below for more details:
> If a socket is in the output readable list, you can be
  as-close-to-certain-as-we-ever-get-in-this-business that a recv on
  that socket will return something.
https://docs.python.org/3/howto/sockets.html#non-blocking-sockets
https://stackoverflow.com/questions/17386487/python-detect-when-a-socket-disconnects-for-any-reason
https://stackoverflow.com/questions/17705239/is-there-a-way-to-detect-that-tcp-socket-has-been-closed-by-the-remote-peer-wit

…n-issues

Co-authored-by: Kekoa Kaaikala <kekoa.kaaikala@gmail.com>

Agent: Add TCPPortSelector

2216 relay bb tests

Previously if the agent couldn't detect the OS, agent failed with errors