Fix Axes Grid rendering in pvbatch
Force Axes Grid to be opaque when batch rendering in symmetric mode
The Axes Grid
labels are translucent, hence by default the label
fragments do not get written to the depth buffer and therefore IceT
skips them when compositing in symmetric mode. This change forces the
entire Grid Axes actor to be opaque so that the labels are composited.
Fixes #17472 (closed).