Don't create native window for sibling widgets

Qt::AA_DontCreateNativeWidgetSiblings attribute prevents other sibling
widgets from creating native window.
It makes sysmgr keep focus of the top level window and handle key events.
    Contributed by KW.L

Also:  DisplayStates was changed to DisplayStateOnLocked after the
timeout period when disabling lock screen.
It blocked delivery of a key event from the virtual keyboard.
    Contributed by Kwangsub Kim.

Open-webOS-DCO-1.0-Signed-off-by: Roger Stringer <roger.stringer@lge.com>

Change-Id: Ie40bb786f679f791ced358ae502554858ee8767d
Reviewed-on: https://g2g.palm.com/1661
Reviewed-by: Build Verification
Tested-by: Roger Stringer <roger.stringer@lge.com>
Reviewed-by: Eric Blade <eric.blade@palm.com>
Reviewed-by: Roger Stringer <roger.stringer@lge.com>