This patch adds the availability_zone attribute to agents and
supports availability_zone API.
Availability_zone support for resources (network/router) and
the schedulers are included in subsequent patches.
APIImpact
DocImpact
Co-Authored-By: IWAMOTO Toshihiro <iwamoto@valinux.co.jp>
Change-Id: Id7a62000ab0484412b3970199df8c374568fe70d
Partially-implements: blueprint add-availability-zone