Merge topic 'qvtk-native-widget-gl-state-fix' into paraview/release

1c218b6d Silence viewport warnings
7e2b618f Remove direct disable of GL_SCISSOR_TEST

Acked-by: Kitware Robot <kwrobot@kitware.com>
Acked-by: Utkarsh Ayachit <utkarsh.ayachit@kitware.com>
Acked-by: Ken Martin <ken.martin@kitware.com>
Merge-request: !4818