Un-harcoding memcached bind address

The patch adds possibility to configure the address
to be bound by memcached server.

Change-Id: Ie808a6e2c96d1b5b6b381ffb689fe0a317eefe23
Related-PROD: PROD-23544
diff --git a/memcached/server/single.yml b/memcached/server/single.yml
index fabef56..7a164c0 100644
--- a/memcached/server/single.yml
+++ b/memcached/server/single.yml
@@ -4,6 +4,7 @@
   memcached:
     server:
       bind:
+        address: ${_param:openstack_memcached_server_bind_address}
         proto:
           tcp:
             enabled: ${_param:openstack_memcached_proto_tcp_enabled}