Fix QListWidget item widget scroll bug

This fix applies the patch uploaded in the bug report. The patch was
provided by Qt-Commercial support but seems to have never found it's
way to the sources although the bug was fixed in Qt 5.

Task-number: QTBUG-27043
Change-Id: I41c5a7b8f3698bb4396046e5e74863e090ba185a
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@digia.com>