DS8K driver: change the design of CG

[OpenStack Infra]

https://review.openstack.org/419321
Dear bug triager. This bug was created since a commit was marked with DOCIMPACT.
Your project "openstack/cinder" is set up so that we directly report the documentation bugs against it. If this needs changing, the docimpact-group option needs to be added for the project. You can ask the OpenStack infra team (#openstack-infra on freenode) for help if you need to.

commit d94651db183c099c81bc3dfc6ebd0688a74fd64c
Author: Jia Min <email address hidden>
Date: Thu Jan 12 01:29:48 2017 -0700

    DS8K driver: change the design of CG

    When making consistency group snapshot, flashcopy in DS8K needs
    to freeze the whole LSS which holds volumes. So it will affect
    volumes not belonging to the CG if they are in the LSS used by
    volumes belonging to CG. In order to dedicate LSS to CG, we need
    to allocate volume not belonging to CG in other LSSs.

    On the other hand, this change switches to generic volume group
    from consistency group at the same time, but generic volume group
    driver interfaces are added in another review, please refer to
    https://review.openstack.org/#/c/445860.

    DocImpact
    Depends-On: Id9964f868c2dc14aaee37e4bcbba330fb4575492
    Closes-Bug: #1655841
    Change-Id: Ic6406a558c035ebb34177f87076adaec55b08f65