disable logging to kscreen.log by default
Summary:
Most of the issues that this feature should uncover have been uncovered,
it makes sense to disable the logging (and futzing around with
QCategorizedLogging) by default, and only use it to debug specific
setups.
Test Plan: Adjusted autotests accordingly.
Reviewers: Plasma, mart
Reviewed By: mart
Subscribers: graesslin, plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D3993