fixed memcached parameter

Change-Id: Icc549046edc6844b801bf7e30a95e8b2a58cc52d
diff --git a/nova/files/mitaka/nova-controller.conf.Debian b/nova/files/mitaka/nova-controller.conf.Debian
index 5d533b6..88589fc 100644
--- a/nova/files/mitaka/nova-controller.conf.Debian
+++ b/nova/files/mitaka/nova-controller.conf.Debian
@@ -124,7 +124,8 @@
 [cache]
 {%- if controller.cache is defined %}
 enabled = true
-memcached_servers={%- for member in controller.cache.members %}{{ member.host }}:11211{% if not loop.last %},{% endif %}{%- endfor %}
+backend = oslo_cache.memcache_pool
+memcache_servers={%- for member in controller.cache.members %}{{ member.host }}:11211{% if not loop.last %},{% endif %}{%- endfor %}
 {%- endif %}
 
 [keystone_authtoken]