Add a active-standby mode memcached in haproxy
Add a active-standby mode memcached in haproxy

Memcached do not support cluster. Then make it work in active-standby
mode. This will be helpful to implement high available when using memcached
as tooz backend.

Change-Id: I13722111d8b8d5b066e9a85d4c8d1679704c8caa

dardelean/kolla-ansible,dardelean/kolla-ansible,dardelean/kolla-ansible