add new states for maas 1.7, and add tests to check mapping

See the comments. maas 1.7 made states more expressive, but only exposes the full set to the node/ api. if you use the nodes/ api, as we do, you get four states folded into the number 6, formerly known as ALLOCATED. (Including a FAILURE state, which is nice).
see here: http://bazaar.launchpad.net/~maas-maintainers/maas/trunk/view/head:/src/maasserver/api/nodes.py#L167

This includes tests to be sure that we get all of them and to be sure that we also do the mapping for 6-> allocated, which is what the rest of our code expects.
at some point in the future they will undo that mapping from the nodes/ api, and we'll have to tweak this more globally.