Deprecates old libvirt config

Icehouse brings a new way to configure libvirt with a dedicated section.
This patch aims to configure libvirt in that way and fails when using
old method.

implement blueprint sync-libvirt-config
closes-bug #1259331

Change-Id: I57438e10d207da7df9c7912c311bac1e7fdfe8aa
Signed-off-by: Emilien Macchi <emilien.macchi@enovance.com>
Merge "Deprecates old libvirt config"