Un-hardcoding horizon server address

The patch makes a possible to change horizon address
which could be used  by horizon by soft param.

Change-Id: Ib4794406612fdb61377ac341314268494b07ee66
Related-PROD: PROD-25528
diff --git a/defaults/openstack/init.yml b/defaults/openstack/init.yml
index 69ff618..2f6d807 100644
--- a/defaults/openstack/init.yml
+++ b/defaults/openstack/init.yml
@@ -59,6 +59,7 @@
     horizon_public_host: ${_param:cluster_public_host}
     horizon_public_port: 443
     horizon_public_protocol: https
+    horizon_server_bind_address: ${_param:single_address}
     # HAproxy
     haproxy_openstack_web_bind_port: ${_param:horizon_public_port}
     #