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: Ibd5decc06f205f5e1de9dbc0d7e9cde5e9435c4e

defaults/main.yml

@@ -191,11 +191,15 @@ barbican_ssl_self_signed_subject: "/C=US/ST=Texas/L=San Antonio/O=IT/CN={{ inter
 #barbican_user_ssl_key: <path to cert on ansible deployment host>
 #barbican_user_ssl_ca_cert: <path to cert on ansible deployment host>
 
+# Memcached override
+barbican_memcached_servers: "{{ memcached_servers }}"
+
 # packages required to run the barbican service
 barbican_pip_packages:
   - barbican
   - osprofiler
   - PyMySQL
+  - pymemcache
   - python-memcached
   - systemd-python
 barbican_user_pip_packages: []

templates/barbican.conf.j2

@@ -148,7 +148,7 @@ username = {{ barbican_service_user_name }}
 password = {{ barbican_service_password }}
 region_name = {{ keystone_service_region }}
 
-memcached_servers = {{ memcached_servers }}
+memcached_servers = {{ barbican_memcached_servers }}
 
 token_cache_time = 300