Comment 9 for bug 43316

I would guess that when you did your dist-upgrade, you didn't have the meta-package ubuntu-desktop installed, right?
You can check this by running these 2 commands from a terminal:
 apt-cache policy gnome-power-manager
 apt-cache policy ubuntu-desktop

To get that power-management preference window I described earlier, you will need to install gnome-power-manager (and possibly reboot your computer afterward).