Adjust scripts to upgrade to Cloud 4

* Include update-status check depending on pacemaker being present
* Write helper-neutron-migration to do the database migrations for neutron
* Extend reboot-nodes to include a mandatory migration step for neutron
* Stop chef-client on the crowbar node at the start of the upgrade process
  and restart it at the end to prevent a zypper lock.
* Extend get_allocated_nodes functionality