Changes for speeding up elabinelab server setup.
Boss/ops/fs: reboot them together after setup rather than serially. Nodes: leave them in PXEWAIT throughout the setup, until after boss has been rebooted. At that point we send them the new bootinfo RESTART command telling pxeboot to re-DHCP and use the new info obtained (next-server) to contact a potentially new boss node. This is a quick way to switch a node in PXEWAIT from talking to the outer boss to talking to the inner one. A significant number of rinky-dink changes were needed to do this, primarily adding a new state, PXELIMBO, where nodes can be sent to sit until they are restarted. It turns out, just putting them in an existing state such as PXEWAKEUP or SHUTDOWN wouldn't work, as they tend to timeout or otherwise reboot.