Couple of small changes resulting from Portal based scaling tests:
1. Do not run the prerender in big experiments. Sucks up a CPU for 15 minutes, just for a jpeg image on the classic interface, that no one is looking at. 2. Do not run vtopgen; this takes a long time too, and since we immediately run the mapper right after, why bother. A small change to mapper will make sure the node counts are set even in alloconly mode, since thats the only reason we run vtopgen in the first place.