Stops the VPCS process.

def stop(self):
        """
        Stops the VPCS process.
        """

        yield from self._stop_ubridge()
        if self.is_running():
            self._terminate_process()
            if self._process.returncode is None:
                try:
                    yield from wait_for_process_termination(self._process, timeout=3)
                except asyncio.TimeoutError:
                    if self._process.returncode is None:
                        try:
                            self._process.kill()
                        except OSError as e:
                            log.error("Cannot stop the VPCS process: {}".format(e))
                        if self._process.returncode is None:
                            log.warn('VPCS VM "{}" with PID={} is still running'.format(self._name, self._process.pid))

        self._process = None
        self._started = False
        yield from super().stop()