Fix up usage statement so that -b,-l options are not accidently used, since they don't do what you expect.
Fix up usage statement so that -b,-l options are not accidently used,
since they don't do what you expect.

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