Xmodem work; bugfixes; reorg.
Xmodem work; bugfixes; reorg.

Allow xmodem reloads if explicitly specified requested via os_load.

Make power cycles asynch; we want to track their outcome via the console.

Make sure to reload switches that have no entries in the partitions
table too.

Misc bugfixes and reorganization.

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