Loading the theme and setting everything up can take a while.
Ensure that we catch all setStage calls that might have been emitted before we were fully up.

CCBUG: 405444

Sabotaged my ksplash theme to take forever to load, did a qdbus setstage call, once ksplash came up and processed the dbus call, the stage immediately advanced without any obvious sideeffects

It's important that the setStage calls are issued without blocking, but startkde script does fire-and-forget, KWin, KSMServer, and Plasma issue an asyncCall,

It is still somewhat racy as startkde launches ksplash --pid which then forks and returns the PID, so there's still a window between startkde reaching the point where it calls kinit has launched and KSplash has started up