Adjust scripts to upgrade to Cloud 4

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
Hrm, please keep the chef-client call: we want to have one run before we start crowbar. I know that on starting the chef-client daemon, there's a run at some point, but we need to wait for it to be over.