Also quit the event loop when a part still holds a reference to a KGlobal object, probably by a KJob which wasn't properly deleted.

This fixes that the Kontact process was still running (without a window) after viewing an article in Akregator.

The real fix would be to fix Akregator, it should take care of properly cleaning up each KJob.

@David: maybe KJob::allowQuitWhileJobsAreRunning(bool) wasn't such a bad idea after all?