Comment 2 for bug 1551954

Reviewed: https://review.openstack.org/284964
Committed: https://git.openstack.org/cgit/openstack/nova-powervm/commit/?id=cb5a4d1cb2fdf0e92d56d1878113f3db825ef83d
Submitter: Jenkins
Branch: master

commit cb5a4d1cb2fdf0e92d56d1878113f3db825ef83d
Author: Kyle L. Henderson <email address hidden>
Date: Thu Feb 25 06:42:54 2016 -0600

    Use LiveMigrateData object

    Nova now sends LiveMigrateData objects exclusively to pass data
    between the compute managers and conductor during live migration.
    Since dicts are no longer supported the conversion to objects
    must be done to continue to support live migration.

    There are multiple parts of this conversion.

    - Create a PowerVMLiveMigrateData object. This object must be
    'registered' in both the compute manager and conductor in order
    for it to be sent over the wire. It can be registered in the
    compute manager by importing it in the compute driver, but for
    conductor there is no way to dynamically load it. This forces
    the use of a unique PowerVM conductor manager for that sole
    purpose.

    - Update the live migration code to return and accept the new
    PowerVMLiveMigrateData object. As part of that conversion, it's
    no longer necessary to pass both a source and destination copy
    of the data. It's now just one object.

    - Update the volume drivers to accept the object. The drivers
    were not using the data provided in most of the object so limit
    them to just a dict of volume data they can originate and
    consume.

    Work not covered:

    - There has been limited real system testing of migration of
    VMs with attached volumes.

    - Updates to the devstack code to enable the PowerVM specific
    version of conductor.

    Partial-Bug: #1551954
    Change-Id: I58e3cd3cf83a5089399b093202d88e17cfcb2bf2