Attached volumes already had support for explicit volume type,
availability zone, and instance locality. Extend this capability to
boot volumes.
(For posterity's sake, a summary of why other options related to
attached volumes were not in fact appropriate for boot volumes:
- volumes_per_node: there can only be one boot volume
- volumes_size: boot volume size given by flavor
- volume_mount_prefix: boot volume handled differently)
Change-Id: I009c0da4179c880fd87a7c1903c93825e8997a38
Story: 2004507
Task: 28229
359b89de3f