Fix regression when multiple items are set to Keys.forwardTo attached
property. QML items accept key events automatically and event should be
by default in accepted state when entering handler.

Task-number: QTBUG-39168
Change-Id: Ibf6c163c4059269996113634efa48ad2fe4d838d
Reviewed-by: J-P Nurmi <jpnurmi@digia.com>