Prevent QEventLoopLocker closing kded unexpectedly

KJobs use QEventLoopLocker under the hood. When a job is destroyed, the
event loop locker will be destroyed and the QGuiApplication object will
be unref'ed. Since isQuickLockEnabled() is true by default, kded will
close, which is not what we want.

To prevent that, set isQuickLockEnabled() to false.