Scaling and speed now depends primarily on os_load (and indirectly,
node_reboot). The time a batch spends in the reload_daemon code appears to
be <1s per node now, instead of taking 30s per node to grab, setup, and
reboot.

Also, finally remove the "obsolete section" that's been sitting in there
for a long time. This was the part that did netdisk reloads, and has
already been neutered out of the code path for several months at least.