session: Move logout sound to end-session phase

[vkareh]

The desktop-logout sound event was being played during the query-end-session phase, which means it would play even if an application inhibited the logout and the user cancelled. Move it to the end-session phase where logout is already confirmed.

[AngryDavid808]

I'll have to compile and test again later, will post back results once I do so. But yes, the update before that was not playing a logout sound or a login sound either, thought I'd post back those results. I used Linux Mint (latest) for the test last time.