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: I19b74c3bc5119953256d3d8f2a98cb5f23787755

defaults/main.yml

@@ -84,6 +84,7 @@ glance_flavor: "{% if glance_default_store == 'rbd' %}keystone{% else %}keystone
 glance_show_image_direct_url: "{{ glance_default_store == 'rbd' }}"
 glance_show_multiple_locations: "{{ glance_default_store == 'rbd' }}"
 
+glance_memcached_servers: "{{ memcached_servers }}"
 
 ## API options
 glance_enable_v2_api: True
@@ -244,6 +245,7 @@ glance_pip_packages:
   - oslo.rootwrap
   - osprofiler
   - PyMySQL
+  - pymemcache
   - python-cinderclient
   - python-glanceclient
   - python-keystoneclient

templates/glance-api.conf.j2

@@ -52,7 +52,7 @@ username = {{ glance_service_user_name }}
 password = {{ glance_service_password }}
 region_name = {{ keystone_service_region }}
 
-memcached_servers = {{ memcached_servers }}
+memcached_servers = {{ glance_memcached_servers }}
 
 token_cache_time = 300
 

templates/glance-registry.conf.j2

@@ -34,7 +34,7 @@ username = {{ glance_service_user_name }}
 password = {{ glance_service_password }}
 region_name = {{ keystone_service_region }}
 
-memcached_servers = {{ memcached_servers }}
+memcached_servers = {{ glance_memcached_servers }}
 
 token_cache_time = 300