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: I64614a02bd3a0d99a69a9c7ac59552ba7cb1fc88

defaults/main.yml

@@ -148,11 +148,15 @@ cloudkitty_pip_packages:
   - msgpack-python
   - osprofiler
   - PyMySQL
+  - pymemcache
   - python-memcached
   - SQLAlchemy>=1.0.10
   - systemd-python
   - tooz
 
+# Memcached override
+cloudkitty_memcached_servers: "{{ memcached_servers }}"
+
 ## (Qdrouterd) integration
 # TODO(ansmith): Change structure when more backends will be supported
 cloudkitty_oslomsg_amqp1_enabled: "{{ cloudkitty_oslomsg_rpc_transport == 'amqp' }}"

templates/cloudkitty.conf.j2

@@ -25,7 +25,7 @@ collector = {{ cloudkitty_collector }}
 connection = {{ cloudkitty_database_connection }}
 
 [keystone_authtoken]
-memcached_servers = {{ memcached_servers }}
+memcached_servers = {{ cloudkitty_memcached_servers }}
 www_authenticate_uri = {{ keystone_service_internaluri }}
 project_domain_id = {{ cloudkitty_service_project_domain_id }}
 project_name = {{ cloudkitty_service_project_name }}