Ubuntu Unity Panel includes menu items Lock and Log Out. But when you click Log Out, you see a dialog box asking if you'd like to Lock or Log Out (a Microsoft-style question for dummies ;-) which I find annoying.
Opening dconf Editor and selecting org > gnome > gnome-session and disabling logout-prompt has no effect, unlike selecting apps > indicator-session and enabling suppress-logout-restart-shutdown, which does what it says -- getting rid of a similar question.
Unfortunately there's no such option yet (as of Ubuntu 16.10).
But it is possible to log out directly by using the keyboard shortcut Ctrl+Alt+Back.