Stops this VirtualBox VM.

def stop(self):
        """
        Stops this VirtualBox VM.
        """

        self._hw_virtualization = False
        yield from self._stop_ubridge()
        yield from self._stop_remote_console()
        vm_state = yield from self._get_vm_state()
        if vm_state == "running" or vm_state == "paused" or vm_state == "stuck":
            if self.acpi_shutdown:
                # use ACPI to shutdown the VM
                result = yield from self._control_vm("acpipowerbutton")
                trial = 0
                while True:
                    vm_state = yield from self._get_vm_state()
                    if vm_state == "poweroff":
                        break
                    yield from asyncio.sleep(1)
                    trial += 1
                    if trial >= 120:
                        yield from self._control_vm("poweroff")
                        break
                self.status = "stopped"
                log.debug("ACPI shutdown result: {}".format(result))
            else:
                # power off the VM
                result = yield from self._control_vm("poweroff")
                self.status = "stopped"
                log.debug("Stop result: {}".format(result))

            log.info("VirtualBox VM '{name}' [{id}] stopped".format(name=self.name, id=self.id))
            yield from asyncio.sleep(0.5)  # give some time for VirtualBox to unlock the VM
            try:
                # deactivate the first serial port
                yield from self._modify_vm("--uart1 off")
            except VirtualBoxError as e:
                log.warn("Could not deactivate the first serial port: {}".format(e))

            for adapter_number in range(0, self._adapters):
                nio = self._ethernet_adapters[adapter_number].get_nio(0)
                if nio:
                    yield from self._modify_vm("--nictrace{} off".format(adapter_number + 1))
                    yield from self._modify_vm("--cableconnected{} off".format(adapter_number + 1))
                    yield from self._modify_vm("--nic{} null".format(adapter_number + 1))
        yield from super().stop()