Update tst_qquickapplication to support OS X ApplicationState handling

This patch modifies tst_qquickapplication so that it tests correctly
against OS X's new ApplicationState handling

Task-number: QTBUG-10899
Change-Id: Iea20b0137daabe03fdddf98435dc2626e122741f
Reviewed-by: J-P Nurmi <jpnurmi@digia.com>