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: Icfb171b7b5bc33bd6f14378003c6fc9bb597837b

defaults/main.yml

@@ -180,6 +180,7 @@ sahara_pip_packages:
   - keystonemiddleware
   - osprofiler
   - PyMySQL
+  - pymemcache
   - python-memcached
   - python-saharaclient
   - python-keystoneclient
@@ -187,6 +188,9 @@ sahara_pip_packages:
   - systemd-python
   - warlock
 
+# Memcached override
+sahara_memcached_servers: "{{ memcached_servers }}"
+
 sahara_optional_oslomsg_amqp1_pip_packages:
   - oslo.messaging[amqp1]
 

templates/sahara.conf.j2

@@ -41,7 +41,7 @@ project_name = {{ sahara_service_project_name }}
 username = {{ sahara_service_user_name }}
 password = {{ sahara_service_password }}
 
-memcached_servers = {{ memcached_servers }}
+memcached_servers = {{ sahara_memcached_servers }}
 
 token_cache_time = 300