Regression: QStyledItemDelegate get wrong rect size for painting

The rectangle passed in QStyledItemDelegate::paint via option.rect is wrongly not adjusted for the vertical scrollbar if the horizontal scroll bar policy is always off.

This triggers a bug in Creator, where we set the horizontal scroll bar to off and paint the whole rect ourselves, see the linked bug report.
A small test case is attached, showing two listviews, with a delegate outputting the option.rect.width(). Both listviews have the same width, but due to the different number of items, one has a scrollbar, whereas the other has no scrollbar. Thus the output by the delegates should differ by the width of the scrollbar. It doesn't though.

This was broken by commit: d91a8f3a5dbcf3e4c4c0afb28463b25e192b00e4 which is only part of qt 4.8 and not in qt 4.7.4