netboot=xnba is deprecated, but profile-based node definitions, the x86
node templates of mkdef --template, the e1350 noderes table and the
SoftLayer importer still gave new x86 nodes xnba. They now give
netboot=ipxe, as node discovery does. Existing nodes keep their method,
and a profile change keeps netboot=xnba on a node that has it: moving a
node to the upstream loader is the choice of the site.
and not available in python 2.6... switched to using docopt for
command line interface argument parsing. This python library is
pulled in by the SoftLayer python bindings so it's not an extra step.