Catch zmq socket_t::bind() failures on startup

Without this zmq socket_t::bind() failure is printed on stdout (and
difficult to track when started in background and with initscript)

Feel free to manage differently, just want to have the error message in logs in case of startup failure (EADDRINUSE).
Only this 3 lines need to be in the try/catch, others don't throw ```zmq::error_t``` since they don't deal with zmq