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: Id853b46de4323b605ff6544b1e48bae30a0bf0a7

defaults/main.yml

@@ -202,6 +202,7 @@ heat_pip_packages:
   - keystonemiddleware
   - osprofiler
   - PyMySQL
+  - pymemcache
   - python-ceilometerclient
   - python-glanceclient
   - python-heatclient
@@ -214,6 +215,9 @@ heat_pip_packages:
   - python-troveclient
   - systemd-python
 
+# Memcached override
+heat_memcached_servers: "{{ memcached_servers }}"
+
 # Specific pip packages provided by the user
 heat_user_pip_packages: []
 

templates/heat.conf.j2

@@ -90,7 +90,7 @@ username = {{ heat_service_user_name }}
 password = {{ heat_service_password }}
 region_name = {{ keystone_service_region }}
 
-memcached_servers = {{ memcached_servers }}
+memcached_servers = {{ heat_memcached_servers }}
 
 token_cache_time = 300