[next][18.08] designate-zone-manager and designate-pool-manager are used despite being deprecated for removal in Rocky

[Dmitrii Shcherbakov]

Although zone manager and designate pool manager were deprecated in Newton and are scheduled for removal in rocky (https://git.io/vhImI), they are still used by charm-designate.

The change can be be observed by comparing Newton architecture diagram https://docs.openstack.org/designate/newton/architecture.html
with the one for Queens:
https://docs.openstack.org/designate/queens/contributor/architecture.html

https://docs.openstack.org/releasenotes/designate/newton.html#upgrade-notes
"To enable designate-worker and designate-producer add a section to your designate.conf called [service:worker] and add an option enabled = True. Then stop designate-pool-manager and designate-zone-manager, and start designate-worker and designate-producer"

https://docs.openstack.org/releasenotes/designate/newton.html#deprecation-notes
"Both designate-zone-manager and designate-pool-manager are now deprecated and will be removed in a future release."

This needs to be taken care of before Rocky to avoid rendering Designate unusable.

[Dmitrii Shcherbakov (dmitriis)]

This will also allow us to potentially stop using memcached as a tooz driver for coordination for designate and gnocchi https://bugs.launchpad.net/charm-designate/+bug/1759597/comments/6 and switch to etcd instead.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/593607

[Ryan Beisner (1chb1n)]

We will also need to do packaging work alongside the charm changes, otherwise the binaries are still on disk, potentially started, running, and unmanaged (by the charm).