Avoid race condition on startup
The activities list needs to be loaded at the time the first DBus call is processed. Otherwise kamd will return an empty list.
updateSortedActivityList was queued as it needs to run after some other code in the main KAMD constructor, but this was racey as we could get DBus traffic in the meantime.
This was relatively easy to hit as this is not in the main thread where the connection is registered and there is a blocking DBus call in the Activies constructor.
(cherry picked from commit 3cbd1b7b)