Use higher max memory for items in memcached

The default max memory is 64MB, which is too small for production
environment.

Change-Id: I72d87cd29762fe49ae4f711f092df655cea954a9
Closes-Bug: #1758286

ansible/roles/memcached/defaults/main.yml

@@ -23,3 +23,6 @@ memcached_image_full: "{{ memcached_image }}:{{ memcached_tag }}"
 # Memcached options
 ####################
 memcached_connection_limit: "5000"
+# NOTE(jeffrey4l): max memory to use for items in megabytes. default is 64MB,
+# which is too small for production environment.
+memcached_max_memory: "256"

ansible/roles/memcached/templates/memcached.json.j2

 {
-    "command": "/usr/bin/memcached -v -l {{ api_interface_address }} -p {{ memcached_port }} -c {{ memcached_connection_limit }} -U 0",
+    "command": "/usr/bin/memcached -v -l {{ api_interface_address }} -p {{ memcached_port }} -c {{ memcached_connection_limit }} -U 0 -m {{ memcached_max_memory }}",
     "config_files": []
 }