test: move TcpProxy to tests/tcp_proxy.py to fix collection - #966

  =================================== FAILURES ===================================
  ___________ HostConnectionTests.test_successful_wait_for_connection ____________
  
  self = <tests.unit.test_host_connection_pool.HostConnectionTests testMethod=test_successful_wait_for_connection>
  
      def test_successful_wait_for_connection(self):
          host = Mock(spec=Host, address='ip1')
          session = self.make_session()
          conn = HashableMock(spec=Connection, in_flight=0, is_defunct=False, is_closed=False, max_request_id=100,
                                      lock=Lock())
          session.cluster.connection_factory.return_value = conn
      
          pool = self.PoolImpl(host, HostDistance.LOCAL, session)
          session.cluster.connection_factory.assert_called_once_with(host.endpoint, on_orphaned_stream_released=pool.on_orphaned_stream_released)
      
          pool.borrow_connection(timeout=0.01)
          assert 1 == conn.in_flight
      
          def get_second_conn():
              c, request_id = pool.borrow_connection(1.0)
              assert conn is c
              pool.return_connection(c)
      
          t = Thread(target=get_second_conn)
          t.start()
      
  >       pool.return_connection(conn)
  
  /project/tests/unit/test_host_connection_pool.py:105: 
  _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
  
  self = <cassandra.pool.HostConnection object at 0x000000004310d948>
  connection = <HashableMock name='mock.cluster.connection_factory()' spec='Connection' id='1125178344'>
  stream_was_orphaned = False
  
      def return_connection(self, connection, stream_was_orphaned=False):
          if not stream_was_orphaned:
              with connection.lock:
                  connection.in_flight -= 1
              with self._stream_available_condition:
                  self._stream_available_condition.notify()
      
          if connection.is_defunct or connection.is_closed:
              if connection.signaled_error and not self.shutdown_on_error:
                  return
      
              is_down = False
              if not connection.signaled_error:
                  log.debug("Defunct or closed connection (%s) returned to pool, potentially "
                            "marking host %s as down", id(connection), self.host)
                  is_down = self.host.signal_connection_failure(connection.last_error)
                  connection.signaled_error = True
      
              if self.shutdown_on_error and not is_down:
                  is_down = True
      
              if is_down:
                  self.shutdown()
                  self._session.cluster.on_down(self.host, is_host_addition=False)
              else:
                  connection.close()
                  with self._lock:
                      if self.is_shutdown:
                          return
                      self._connections.pop(connection.features.shard_id, None)
                      if self._is_replacing:
                          return
                      self._is_replacing = True
                      self._session.submit(self._replace, connection)
  >       elif connection in self._trash:
               ^^^^^^^^^^^^^^^^^^^^^^^^^
  E       TypeError: __hash__ method should return an integer not 'MagicMock'