Fix a pclass bug - we weren't correctly handling the case where one pnode's types were a subset of another's.
Fix a pclass bug - we weren't correctly handling the case where one
pnode's types were a subset of another's.

nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome