This patch creates compute RPC API version 4.0, while retaining
compatibility in rpcapi and manager for 3.x, allowing for
continuous deployment scenarios.
UpgradeImpact - Deployments doing continuous deployment should follow this
process to upgrade without any downtime:
1) Set [upgrade_levels] compute=kilo in your config.
2) Upgrade to this commit.
3) Once everything has been upgraded, remove the entry in
[upgrade_levels] so that all rpc clients to the nova-compute service
start sending the new 4.0 messages.
Change-Id: Id96e77c739e7473774e110646204520d6163d8a5