Instance delete always stops partition even if partition ia already stoped.

[Prabhat Ranjan]

When partition is in shutoff state and then if I try to delete partition then throwing error

HTTPError: 409,1: The partition is not in a valid state to perform the operation [POST /api/partitions/c4ee7834-5d63-11e7-a035-42f2e9ef1641/operations/stop]

Work around should be.
1. If partition is already stop then don't stop it again. Just delete it.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/479240

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/479240
Committed: https://git.openstack.org/cgit/openstack/nova-dpm/commit/?id=4c23e0b0bcfec32c2fda762d01663280a1f55afa
Submitter: Jenkins
Branch: master

commit 4c23e0b0bcfec32c2fda762d01663280a1f55afa
Author: Prabhat Ranjan <email address hidden>
Date: Fri Jun 30 15:28:09 2017 +0530

    Instance delete always stops partition

    Instance delete always stops partition even if partition ia already stoped.
    Work around is when it try to stop the partition which
    is already stopped, then catch exception and pass it.

    Closes-Bug: #1701506

    Change-Id: I8ddb84de307bc58fa68136c503408a2d65ef629a
    Signed-off-by: Prabhat Ranjan <email address hidden>