Reboot handler cleanup

> I apologize, I just realized something: we need to wait for crowbar_join to succeed on the reboot. That means that the node should be back to "ready" state; if it reaches the "problem" state, then it failed applying. And we should probably exit with 1.

With https://github.com/toabctl/barclamp-crowbar/commit/8399038c6c0baf5df7012a681c8fa5c5b3745c8c I fixed the possible race if you try to get the uptime from a host. Checking that the node is back in "ready" state is the next thing.
Is there somewhere a list with possible node states?