Comment 2 for bug 1576048

Reviewed: https://review.openstack.org/310691
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=34b8336a41e2896f0639c402f64a05247f475fea
Submitter: Jenkins
Branch: master

commit 34b8336a41e2896f0639c402f64a05247f475fea
Author: Wenzhi Yu <wenzhi_yu@163.com>
Date: Thu Apr 28 16:06:57 2016 +0800

    Make compute rpcapi 'live_migration' backward compatible

    This commit[1] added compute rpcapi version 4.2 which introduced a new
    argument 'migration' when calling 'live_migration' method, but the code
    did not ensure the backward compatibility with older version compute
    node.

    When calling 'live_migration' method with 'migration' argument on older
    version(like Kilo) of nova compute node, a "TypeError: live_migration()
    got an unexpected keyword argument 'migration'" will be threw up.

    [1]https://github.com/openstack/nova/commit/2f4e64a7cf81de4a22fe2fc4210b1f795b1a3db4

    Change-Id: Ie5c498d34e7c4c6573d611abd592c25f1bcb4f44
    Closes-Bug: #1576048