Explicitly pass the keyfile to tevc invocations.
Explicitly pass the keyfile to tevc invocations.

This will used the local copy of the keyfile (/var/emulab/boot) instead
of the across-NFS copy (/proj/.../tbdata).

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