Blender Git Loki

Fix T53048: OSL Volume is broken in Blender 2.79

Was a mistake in optimization commit which was disconnecting closures and nodes
which does not make sense for volume output.

OSL script we can't ignore and can't currently know in advance if it's a proper
volume shader or not. So we never disconnect OSL nodes from volume output.

This is a good candidate for corrective release.