Use dbus-run-session instead of dbus-launch --exit-with-session
Summary:
dbus-launch --exit-with-session behaves badly if there's no X server running.
This resulted in it breaking when being launched from gdm or lightdm.
Also, the manpage explicitly states "This option is not recommended".
Test Plan:
Using it right now, started with sddm.
Also verified that nothing remains after logout.
Reviewers: Plasma, davidedmundson
Reviewed By: Plasma, davidedmundson
Subscribers: plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D11478
[cherry-picked from 19bee4105feb3e8de0fc1e170bf36260d6c2b3b2 which got
lost due to scripty conflicts]