connection refused should terminate query collection

If resolver refuses TCP connection, orchestrator should exit.

ConnectionRefusedError: [Errno 111] Connection refused
Traceback (most recent call last):
  File "/usr/lib/python3.5/multiprocessing/process.py", line 249, in _bootstrap
    self.run()
  File "/usr/lib/python3.5/multiprocessing/process.py", line 93, in run
    self._target(*self._args, **self._kwargs)
  File "/usr/lib/python3.5/multiprocessing/pool.py", line 103, in worker
    initializer(*initargs)
  File "/home/pspacek/respdiff/respdiff/sendrecv.py", line 81, in worker_init
    worker_reinit()
  File "/home/pspacek/respdiff/respdiff/sendrecv.py", line 85, in worker_reinit
    selector, sockets = sock_init()  # type: Tuple[Selector, ResolverSockets]
  File "/home/pspacek/respdiff/respdiff/sendrecv.py", line 186, in sock_init
    sock.connect(destination)
  File "/usr/lib/python3.5/ssl.py", line 1019, in connect
    self._real_connect(addr, False)
  File "/usr/lib/python3.5/multiprocessing/process.py", line 249, in _bootstrap
    self.run()
  File "/usr/lib/python3.5/ssl.py", line 1006, in _real_connect
    socket.connect(self, addr)
  File "/usr/lib/python3.5/multiprocessing/process.py", line 93, in run
    self._target(*self._args, **self._kwargs)
  File "/usr/lib/python3.5/multiprocessing/pool.py", line 103, in worker
    initializer(*initargs)
  File "/home/pspacek/respdiff/respdiff/sendrecv.py", line 81, in worker_init
    worker_reinit()