This fact caused by the qt signal-slot implementation. Even if slots
code is going into parallel they will be called in the main app thread.
And also it is used inside KF5 dataengine implementation, so I'm affraid
that it could not be optimized w\o backend rewriting
* create QTimer object in AWDataEngineAggregator class, emit signal to
this timer because timers could not be started in the separate thread
* increase limit x2 with leaving the thread pool size as was