Adjust scripts to upgrade to Cloud 4

* Handle possible absence of barclamp-pacemaker on a non-HA setup
* Write helper-neutron-migration to do the database migrations for neutron
* Rename reboot-node to prepare-and-reboot-nodes and extend it
> Not in my dev setup that was installed with mkcloud and cloudsource=susecloud3

Did you install all cloud3 updates? I my setup it is installed. Having all Cloud 3 update installed is a strict requirement for being able to upgrade to Cloud 4.