[REG 4.8.6->5.0.0] QScrollBar emits valueChanged twice if slot takes too much time

Attached application simulates some heavy processing by using Sleep(1000) and it causes double valueChanged signal.

Steps:
-Build and run the example application
-Press scrollbar to right once
-Close the application and check the hit count(printed via qDebug)

Actual result:
-Hit count is 2

Expected result:
-Hit count is 1