* Change dns backends and pools.yaml to use
ipv6 addresses not wrapped in brackets.
* Changed MySQL backends to use MYSQL_HOST.
* Fixed bug in pdns4 driver not allowing
masters to use an ipv6 address.
Depends-On: https://review.opendev.org/#/c/678324/
Change-Id: I8f469e732618732f5417c1b5e6c2049eaa83ea78
* Add a new backend for DevStack allowing the Agent
backend to be configured.
* Change the agent to choose a sane port by default, it's extremely
unlikely anyone is exposing the agent on port 53 intentionally.
* The agent itself is not yet configured, this will come later as it
involves refactoring most of the BIND non-agent backend into a lib.
* Fail when the user asks for the agent backend, without also enabling
the agent service.
Change-Id: Iedde58f4f5a2ea89cb9da78aaec1853208af8fc9