pubsubd wasn't restarting, surely because the existing pubsubd was still
running and/or socket state was still live in the kernel even after
putative death.  This took a long time to manifest, and it's not clear
exactly what the problem was, but making sure pubsubd is dead (and is no
longer holding its specific port) is appropriate even if we assume
REUSEADDR is working, and fixes the current problem.  This was only
observable on the pc3000s and c220g2s, as far as I saw.