Bug#1004680: upgrade-reports: beep when selecting logout

[Akbarkhon Variskhanov <akbarkhon.variskhanov@gmail.com>]

Control: forwarded -1 gitlab.xfce.org/xfce/xfce4-session/issues/146
Control: reassign -1 xfce4-session
Control: tags -1 - d-i + wontfix

As suggested in the upstream issue, you need to set the
/general/ShowScreenshots to false like so:

$ xfconf-query --channel xfce4-session --property
/general/ShowScreenshots --set false

The part of code responsible for emitting the beep has been around for
a long time. It's done so as to notify of a taken screenshot, which is
used to represent the current session in the list of saved sessions.

You could argue that it should be disabled by default but I guess it's
better to provide some feedback and let the user know.