background-color needs to be set for QMenuBar::item as well in WindowsVista style to obtain a fully colored menu bar

The attached example can be used to reproduce the issue.

Steps to reproduce:
1. run the example
2. check the "Menu" item background color

Expected result:
The "Menu" item background should be red

Actual result:
The "Menu" item background is not red

As a workaround one can set the stylesheet like this:

menuBar.setStyleSheet(QStringLiteral("QMenuBar , QMenuBar::item { background-color: rgb(255, 0, 0); }"));