Fix T38192: OSL got incorrectly enabled in preview render when GPU was selected for rendering of the main scene.
Fix T38192: OSL got incorrectly enabled in preview render when GPU was selected
for rendering of the main scene.

tangent-opensource/coreBlackbird,tangent-opensource/coreBlackbird,tangent-opensource/coreBlackbird,pyrochlore/cycles,pyrochlore/cycles,pyrochlore/cycles