libvirt: Support volume snapshot creation for libgfapi-attached volumes

[Eric Harney]

Nova requires changes to support creation of snapshots for attached volumes that are connected via libgfapi. This change is in line with recent developments to support this feature in libvirt.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/78748

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/78748
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=124c9b682651610c3d31059186401f5342a9ddcd
Submitter: Jenkins
Branch: master

commit 124c9b682651610c3d31059186401f5342a9ddcd
Author: Eric Harney <email address hidden>
Date: Thu Oct 24 12:56:21 2013 -0400

    libvirt: Support snapshot creation via libgfapi

    Currently, the libvirt driver only handles volume snapshot
    creation for file-backed volumes.

    This changes allows volume snapshot creation for libgfapi-
    attached volumes to work. (A sufficiently new version of
    libvirt is required.)

    Implements: blueprint libvirt-volume-snap-network-disk
    Closes-Bug: 1288976

    Change-Id: Ic6dd861b40b692b25df67c9d5b63fd436c690fde