QNX: Surpress manual window activation during showFullScreen

When a window is shown, libscreen will give it keyboard focus.
Requesting the activation right after the window is created (and
before libscreen activated the window) causes problems on some devices
e.g. Q10.

Change-Id: I29f7a38990ea4259a8b0c6624f70e31d7291af00
Reviewed-by: Sergio Ahumada <sahumada@blackberry.com>