Skip OVG tests on boot2qt

Loading OVG is unstable on qemu. That needs to be skipped for
boot2qt tests.

This will conflict when merging to branch 5.10 with commit
c341b2b2

. Correct version is in
5.10.

Task-number: QTBUG-63079
Change-Id: Ic691beb3dbbfdc64ca31b380ad85d9dadbe08a90
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>