Minor bug fix; inner_elab_role will be NULL for the firewall node, so skip that instead of core dumping.
Minor bug fix; inner_elab_role will be NULL for the firewall node, so
skip that instead of core dumping.

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