Add the beginnings of the nova-conductor service
Add the beginnings of the nova-conductor service

This adds a new service called "nova-conductor" which will provide
services for nova-compute, such as completing database updates and
handling long-running tasks.

Right now, this just adds a fraction of the database-related work
so that we can proceed with incremental changes to nova-compute.

For compatibility/flexibility, both LocalAPI and (RPC)API classes
are provided. Users concerned with performance or compatibility
who wish to maintain compute-node-local database accesses can
set the [conductor] use_local=True, which will mimic the legacy
behavior.

DocImpact

Change-Id: Ib81d879f40b7daceeffad5af0631c7db68168661

n0ano/ganttclient