Start the monitor.

def start_monitor(self):
        """Start the monitor."""
        stdout_file, stderr_file = self.new_log_files("monitor")
        process_info = ray.services.start_monitor(
            self._redis_address,
            stdout_file=stdout_file,
            stderr_file=stderr_file,
            autoscaling_config=self._ray_params.autoscaling_config,
            redis_password=self._ray_params.redis_password)
        assert ray_constants.PROCESS_TYPE_MONITOR not in self.all_processes
        self.all_processes[ray_constants.PROCESS_TYPE_MONITOR] = [process_info]