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

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

Test Plan: reboot with zanshin open

Reviewers: dvratil

Reviewed By: dvratil

Subscribers: kde-pim, #kde_pim

Tags: #kde_pim

Differential Revision: https://phabricator.kde.org/D3788