[REG 4->5] After closing a popup menu, hover effects of widgets are broken.

After closing a popup menu by clicking on a screen area outside the menu, mouse hover handling is broken. You have to click on the window again to fix it.

Steps to reproduce:
1. Open any one Qt5 program with context menus
2. Open the context menu using right mouse button or keyboard shortcuts
3. Click on any place outside the popup menu to close it
4. Move the mouse cursor over any buttons, line edit controls, or widgets that changes their styles on hover defined by the widget style.

Expected behavior:
The buttons should change their style on mouse hover if it's defined in the QStyle or Qss rules.

Actual behavior:
The buttons or other widgets do not change their look, just like they do not receive the mouse hover events at all. After clicking on the program window again, mouse hover effects become normal again.

If you close the popup menu using "ESC" key rather than mouse click, the bug won't be triggered.

This bug does not exist in Qt 4. We noted this problem after upgrading to Qt 5.4. It's a very annoying regression bug.