Comment 8 for bug 1709739

Reviewed: https://review.openstack.org/492969
Committed: https://git.openstack.org/cgit/openstack/tempest/commit/?id=5805d32137d6b930244b06a7f8373c167c35cb26
Submitter: Jenkins
Branch: master

commit 5805d32137d6b930244b06a7f8373c167c35cb26
Author: xing-yang <email address hidden>
Date: Fri Aug 11 04:31:27 2017 -0700

    Volume and group on same backend in update_group

    In a multiple backend environment, a volume can be created
    on a different backend from a group, add volume to group
    will fail in this case. The 'host' field of a volume or a
    group is an internal field that cannot be retrieved by
    using Cinder volume APIs. The only way to make sure a volume
    is created on the same backend as the host is to create the
    volume with the group_id parameter. After that remove the
    volume from the group, and then add the volume back to the
    group. This way the volume to be added to the group will be
    on the same backend as the group.

    This will make the test longer than desired, but it is
    the only way to make sure the added volume is on the same
    backend as the group.

    Change-Id: I376f0188984d706e83740f67bd6f301f680914f8
    Closes-Bug: #1709739