Fix handling of volume copy for ‘virtual’ volumes

[Nikesh]

Dot Hill volumes allocated from virtual storage pools require different handling than volumes allocated from vdisks when cloning volumes or snapshots. This change ensures that the correct API calls are used based on the backend_type property declared in the cinder.conf.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/217615

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/217615
Committed: https://git.openstack.org/cgit/openstack/cinder/commit/?id=2899d4624e2b07933bbe1237cd25ab73f27f53f6
Submitter: Jenkins
Branch: master

commit 2899d4624e2b07933bbe1237cd25ab73f27f53f6
Author: nikeshm <email address hidden>
Date: Thu Aug 27 15:29:02 2015 +0530

    Fix volume copy for 'virtual' volumes in DotHill

    Dot Hill volumes allocated from virtual storage pools require
    different handling than volumes allocated from vdisks when
    cloning volumes or snapshots.

    This change ensures that the correct API calls are used based on
    the dothill_backend_type property declared in the cinder.conf.

    Change-Id: If2ac15d1d6426948ff439815e85411fbbb95215b
    Closes-Bug: #1489303
    Co-Authored-By: Chris Maio <email address hidden>
    Co-Authored-By: Lakshman <email address hidden>