Fix RenderNode autotest on BlackBerry

On BlackBerry the first window that is created is always shown as fullscreen.
This is a platform restriction and possibly applies to other platforms as well.
The autotest however expects the window to be of a specific size.
As workaround a "container" window is created first in which the QQuickView is placed.

Change-Id: Ib9023cfcb9148c6cafb21872c2821ebcb8fd664f
Reviewed-by: Alan Alpert (Personal) <416365416c@gmail.com>