Cinder Provider could not distinguish two Cinder volume with the same name and metadata(volume_from)

[dengshaolin]

For method fuxi.volumeprovider.cinder.Cinder._get_docker_volume,
It just return the first Cinder volume if find with search_opts,
or None if not find.
But for Fuxi only one volume could exist on backend with the same
name and metadata which contains key 'volume_from', so when find
more than one matched Cinder volume, this method should raise an
exception.

[OpenStack Infra (hudson-openstack)]

Change abandoned by dengshaolin (<email address hidden>) on branch: master
Review: https://review.openstack.org/384456

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/387937
Committed: https://git.openstack.org/cgit/openstack/fuxi/commit/?id=1d25d35f4f7125adb75c59993668537e3696bd9c
Submitter: Jenkins
Branch: master

commit 1d25d35f4f7125adb75c59993668537e3696bd9c
Author: drngsl <email address hidden>
Date: Tue Oct 18 07:11:11 2016 -0400

    Raise exception when find more than one matched Cinder volumes

    For method fuxi.volumeprovider.cinder.Cinder._get_docker_volume,
    It just return the first Cinder volume if find with search_opts,
    or None if not find.
    But for Fuxi only one volume could exist on backend with the same
    name and metadata which contains key 'volume_from', so when find
    more than one matched Cinder volume, this method should raise an
    exception.

    Change-Id: I6b4af9151363a3b6de8294b836f0a46e64566245
    Closes-Bug: #1631925