When setting the warning/error icon on a Qt version in the Qt options
page: Do not send dataChanged if the icon has not actually changed.

This fixes the selection getting broken when two Qt versions happen to
have the same displayName.

Task-number: QTCREATORBUG-16644
Change-Id: I7722fbc021388be237e59a59bd136c61f611ad52
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>