Add ability to deploy designate and pdns on different nodes

Currently old designate pdns backend class implicitly includes
powerdns server, this won't allow to deploy designate and pdns
on different nodes.
Also simple.yml is split so it is possible to configure do
pools configurations.

Change-Id: Ib717d4a124686c1d36ef83642bbaadcda0d8bf66
Related-Prod: https://mirantis.jira.com/browse/PROD-18317
7 files changed