[qe-core] turn_off_kde_screensaver does not turn off energy saving
turn_off_kde_screensaver function in
lib/x11utils.pm only disables the screenlocker but not the the energy saving. This is causing long running tests to fail because the VNC screen goes black.
AC1: Add the capability to disable energy saving for the plasma desktop.
Investigate if there is a similar issue for GNOME.
This blocks poo#101881 because a long update can trigger the energy saving.