QtQuick test: Do not complain about Qt specific arguments

QtQuick test: Do not complain about Qt specific arguments

Commit 1ca5e82cccae0 caused a regression for Qt arguments like
-qmlsjsdebugger=xxx . These are automatically removed from argv by
QCoreApplication, but since we copied argv before instantiating
QCoreApplication this didn't have any effect.

Fix this by moving Q[Core]Application instantiation again before
the parsing and copying of testlib-specific arguments.

Task-number: QTBUG-37793
Change-Id: Ief41640b6cf3251f700a5d24d2e1141233a3888f
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Reviewed-by: Liang Qi <liang.qi@digia.com>