Prophet storage failed to re-detach volume when volume already detached in back-end storage

[Rick Chen]

When first request command to request detach volume, but the back-end storage in-processing. Next retry command will got the volume already detached error code to make cinder receive error.

VolumeBackendAPIException: Bad or unexpected response from the storage volume backend API: Flexvisor unassign volume failed:9fd296a1-8e4b-4753-8449-6ef0eb03dc18:61.
<158>Sep 24 02:35:04 node-3 <feff>cinder-cinder.api.middleware.fault INFO: http://172.16.0.4:8776/v1/dd27dade8bc345b5be9b4caf8a28ef32/volumes/9fd296a1-8e4b-4753-8449-6ef0eb03dc18/action returned with HTTP 500

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/123664

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/123664
Committed: https://git.openstack.org/cgit/openstack/cinder/commit/?id=7a5383a70adce0a6284c9c10a0d352077aa9edea
Submitter: Jenkins
Branch: master

commit 7a5383a70adce0a6284c9c10a0d352077aa9edea
Author: Rick Chen <email address hidden>
Date: Wed Sep 24 17:08:52 2014 +0800

    Failed to re-detach volume when volume detached.

    When first request command detach the volume, but the back-end
    storage state is in-processing or busy. Next retry command will
    got the error code that describe the volume already detached.

    Change-Id: If340980ab2dcc844398254ff368ca6b78ca40ff6
    Closes-Bug: 1373317