* tb-set-node-sharingmode{node mode} sets the sharing mode for a
  physical node. Only admins can do this, to create an experiment to
  contain shared nodes.

* tb-set-node-usesharednode{node weight} sets a desire to use a shared
  node (for a pcvm). This goes into assign, against the a feature that
  is set for all nodes actining as a shared host.