Fix ServerManager going into Broken state when called before going to the event loop.

Symptom: zanshin was coming up empty when session-restored.

Test Plan: reboot with zanshin open

Reviewed By: dvratil
Differential Revision: https://phabricator.kde.org/D3788

(cherry picked from commit 9cb74e7111c42d96f8cf8062319561c29431c4c9)