Given what you are trying to do, I suspect that you do not need to reboot. I think you just need to restart X. Logging out doesn't do this, but I think restarting LightDM might. Try
$ sudo systemctl restart lightdm
Given what you are trying to do, I suspect that you do not need to reboot. I think you just need to restart X. Logging out doesn't do this, but I think restarting LightDM might. Try
$ sudo systemctl restart lightdm