The event loop provided by sync::network::Service.run() will exit if there are no more pending items to be run. This resulted in having to create a long running timer called keep_running_timer in the Sync Client that was always active so there was something to do for the event loop to prevent it from exiting prematurely.

Update Service so it can be constructed with an optional bool value that removes the requirement for something to keep the event loop "primed" so it doesn't exit if there is nothing to do. Once this is implemented, the keep_running_timer can be removed.