Use node.run_state[:reboot] to trigger reboots

This is much safer than rebooting from the recipe.

This works because we install a reboot handler in crowbar_join.suse.sh.
Log that we are rebooting
Fix recipe to use correct attribute to know when to reboot

We were simply never rebooting.
Merge pull request #3 from vuntz/rework-reboot

Use node.run_state[:reboot] to trigger reboots