Add version 2.0 of compute RPC API
Add version 2.0 of compute RPC API

RPC API versioning is helpful because (a) it gives useful error messages
if there is a version mismatch and (b) it allows you to update to a new
version of the API on the server side before updating the client side.

However, we still regularly encounter DB changes which force the client
and server side to be updated together. This will not be resolved until
no-db-compute is fully implemented.

It's safe to say that RPC API clients using version 1.0 will not work
with a version 1.44 compute manager (because of DB schema changes). The
issue, then, is that continuing to support 1.0 clients in the Folsom
release seems pointless and the alternative of removing legacy RPC API
support would mean a lot less cruft code in the release.

Before removing version 1.x of the compute RPC API, we add version 2.0
while still retaining 1.x support. This gives users the option of
upgrading all compute RPC API users to use version 2.0 before version
1.x support is removed from compute nodes.

Change-Id: I1c74b36a84d770b0af5ca33062e069a545537ee2

n0ano/gantt,n0ano/gantt