Bug Fix: require "pubsub" not "pubsubd" to match the pubsub startup script.
Bug Fix: require "pubsub" not "pubsubd" to match the pubsub startup script.

Otherwise, pubsubd won't start til after the testbed startup. Since
checknodes_daemon wants to send an event, it will hang forever if pubsubd
is not running.

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