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]2f4e64a7cf
Change-Id: Ie5c498d34e7c4c6573d611abd592c25f1bcb4f44
Closes-Bug: #1576048
(cherry picked from commit 34b8336a41)