Add new capability to API for a node to report its current runlevel.

Add new capability to API for a node to report its current runlevel.
Additional motivation is available in message to devel@lists.planet-lab.org:
	http://lists.planet-lab.org/pipermail/devel/2009-February/003283.html

Briefly:
	this patch differentiates between boot_states (declared by user) and
	run_levels (reported by node) a user would specify that the node should be
	in 'boot' or 'reinstall', and the node will report what state it is in,
	i.e, it is installing, or it has failed to boot, or it is in boot.

	because updates are continuous, other service routines can get involved to notify
	admins, users, or automated scripts when the values are out-of-sync.