* Various improvements to new node stuff, including reworking node
  status updates so that they use the right table, and don't update
  vnodes that are alive (since their watchdog will do this).

* Added renewal code to automatically renew all leases that are doing
  to expire within two days.

* Moved Emulabification directly into the node abstraction.  Now the
  libplab wrapper scripts are all just plain wrapper scripts, instead
  of having the knowledge spread out

* Switched from using a Plab-specific keypair to using the normal
  Emulab one, which makes it possible to use sshtb to Plab nodes.

* Removed node booting code, since vnode_setup takes care of this.