Add Disk Capacity in cluster-data-model

[Jean-Emile DARTOIS]

Even if the blueprint cluster-model-objects-wrapper will add the possibility to fetch the information need by the strategies through the openstack clients. The strategy "ZHAW" is approved in the next watcher release and needs the disk capacity of a compute node.
This information is not available in the current version of watcher. ( no capacity but free_disk_gb)

We need to fetch this information from nova and add this attribute in the watcher-cluster-data-model.

https://github.com/openstack/watcher/blob/master/watcher/metrics_engine/cluster_model_collector/nova.py#L57

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/288465

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/288465
Committed: https://git.openstack.org/cgit/openstack/watcher/commit/?id=681536c8c7156c8326dbabbe21c9a4129ec38f32
Submitter: Jenkins
Branch: master

commit 681536c8c7156c8326dbabbe21c9a4129ec38f32
Author: Bruno Grazioli <email address hidden>
Date: Fri Mar 4 14:50:07 2016 +0100

    Added Disk Capacity in cluster-data-model

    Fetched information of total disk capacity from nova and added a new
    resource 'disk_capacity' to NovaClusterModelCollector cluster. Also a
    new resource type 'disk_capacity' was added to ResourceType.
    https://bugs.launchpad.net/watcher/+bug/1553124

    Change-Id: I85750f25c6d2693432da8e5e3a3d0861320f4787
    Closes-Bug: #1553124