OutputPanes::hasFocus() needs to check the window's focus widget

QWidget::hasFocus() returns false if the window isn't active.

Task-number: QTCREATORBUG-13361
Change-Id: I7152ec2139bbb255c2a722e378a111dc4bc2ed62
Reviewed-by: Eike Ziller <eike.ziller@theqtcompany.com>