Disable DBusTest temporarily due to buildbot issue

This test fails on kf5-qt5 SUSEQt5.9 buildbot since Oct 28, 2018
Believed due to frameworks regession; disable to avoid sysadmins having
to fix for every build
https://mail.kde.org/pipermail/kde-frameworks-devel/2018-November/073078.html
https://phabricator.kde.org/T9948