* The Emulab portal now adds a toplevel element (Emulab namespace)
  directing the CM to use standard emulab mounts (read: /users).
  We clear that element from the other portals.

* The CM looks for that tag, and allows it only if the caller is the local
  SA. The default for nfsmounts setting for geni experiment containers is
  "genidefault", but that is set to "emulabdefault" when allowed.

* tmcd changes; no using nfsmounts slot instead of nonfsmounts. "none"
  means no mounts (duh), "emulabdefault" means standard mounts we all know
  and love, "genidefault" means no /users mounts.

  In addition, when we are doing emulabdefault mounts on a geni experiment
  node, we do not return accounts that are specified in the rspec, but
  rather we return the local project accounts only.