Build an observer image for Debian

[eroussy]

Abstract
To harmonize Yocto and Debian SEAPATH, an observer Debian image should also be provided.

Current status
When using a Debian cluster with an observer machine, the standard hypervisor image is used

Detailed Description
The Yocto flavor of SEAPATH proposes two different images : hypervisor and observer.
The observer is used in a cluster with two hypervisors, as a low-price third machine to form the quorum.
This observer machine is an hypervisor machine without virtualisation

Work to be done

• separate virtualization packages in FAI
• Update documentation to build observer (hypervisor image without virtualization)
• Update cukinia tests to not test virtualization on observers.