Fix "error activiting kdeconnectd" for kdeconnect-cli

Summary:
Kdeconnect-cli always displayed one or more "error activating kdeconnectd: QDBusError("", "")" messages.

This diff uses the reply of starting the kdeconnect daemon correctly, so this does not happen anymore.

Test Plan: Kdeconnect-cli and the daemon still work, but kdeconnect-cli does not show the error message anymore. I verified that if, for some reason, the daemon could not start, it does display an error.

Reviewers: KDE Connect, apol

Reviewed By: KDE Connect, apol

Subscribers: apol

Differential Revision: https://phabricator.kde.org/D9058