Add DB check to make sure the os image spec is valid (in the DB, and appropriate for the node type). This prevents the user from editing the IR file directly and specifying a bogus image ID.
Add DB check to make sure the os image spec is valid (in the DB, and
appropriate for the node type). This prevents the user from editing
the IR file directly and specifying a bogus image ID.

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