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: Ifedee3b46a845b66d54279b5a35edd16faa80e05

defaults/main.yml

@@ -155,6 +155,7 @@ octavia_pip_packages:
   - keystonemiddleware
   - osprofiler
   - PyMySQL
+  - pymemcache
   - python-glanceclient
   - python-keystoneclient
   - python-memcached
@@ -166,6 +167,9 @@ octavia_pip_packages:
   - shade
   - systemd-python
 
+# Memcached override
+octavia_memcached_servers: "{{ memcached_servers }}"
+
 # Specific pip packages provided by the user
 octavia_user_pip_packages: []
 

templates/octavia.conf.j2

@@ -93,7 +93,7 @@ password = {{ octavia_service_password }}
 region_name = {{ keystone_service_region }}
 auth_type = password
 endpoint_type = {{ octavia_clients_endpoint }}
-memcached_servers = {{ memcached_servers }}
+memcached_servers = {{ octavia_memcached_servers }}
 
 token_cache_time = 300
 
@@ -314,7 +314,7 @@ username = {{ octavia_service_user_name }}
 password = {{ octavia_service_password }}
 region_name = {{ keystone_service_region }}
 auth_type = password
-memcached_servers = {{ memcached_servers }}
+memcached_servers = {{ octavia_memcached_servers }}
 endpoint_type = {{ octavia_clients_endpoint }}
 token_cache_time = 300