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: I06993827240135365c83bbfd4a75712598a2310a

defaults/main.yml

@@ -211,11 +211,15 @@ manila_pip_packages:
   - keystonemiddleware
   - osprofiler
   - PyMySQL
+  - pymemcache
   - python-openstackclient
   - python-memcached
   - systemd-python
   - uwsgi
 
+# Memcached override
+manila_memcached_servers: "{{ memcached_servers }}"
+
 manila_user_pip_packages: []
 
 manila_optional_oslomsg_amqp1_pip_packages:

templates/manila.conf.j2

@@ -78,7 +78,7 @@ username = {{ manila_service_user_name }}
 password = {{ manila_service_password }}
 region_name = {{ keystone_service_region }}
 
-memcached_servers = {{ memcached_servers }}
+memcached_servers = {{ manila_memcached_servers }}
 
 token_cache_time = 300
 
@@ -117,4 +117,4 @@ region_name = {{ cinder_service_region | default(manila_service_region) }}
 project_name = {{ cinder_service_project_name | default("service") }}
 username = {{ cinder_service_user_name | default("cinder") }}
 password = {{ cinder_service_password }}
-{% endif %}
+{% endif %}