Refactor memcached_servers

This patch aims to add a prefix for memcached_server
on each role to give the ability for deployers to
override the location of memcached cluster. I.e users
wants to create a single memcached cluster with k8s
for each service.

We also add pymemcache based on [1]

[1] https://review.opendev.org/711429

Change-Id: Ic83f6371c5d2bbed6a7d6d2f92a69fd3a2afd0d3

defaults/main.yml

@@ -294,6 +294,7 @@ cinder_pip_packages:
   - keystonemiddleware
   - osprofiler
   - PyMySQL
+  - pymemcache
   - python-openstackclient
   - python-memcached
   - systemd-python
@@ -385,3 +386,5 @@ cinder_environment_overrides:
     Environment: "PATH={{ cinder_bin }}:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
 
 _UUID_regex: "[0-9a-f]{8}-([0-9a-f]{4}-){3}[0-9a-f]{12}"
+
+cinder_memcached_servers: "{{ memcached_servers }}"

templates/cinder.conf.j2

@@ -152,7 +152,7 @@ username = {{ cinder_service_user_name }}
 password = {{ cinder_service_password }}
 region_name = {{ keystone_service_region }}
 
-memcached_servers = {{ memcached_servers }}
+memcached_servers = {{ cinder_memcached_servers }}
 
 token_cache_time = 300