Add apache metadata to horizon classes

Change-Id: I830b123d79f5a24d959f7cc7da940fc5c1932cba
Related-Prod: PROD-16189
diff --git a/horizon/server/cluster.yml b/horizon/server/cluster.yml
index a68ab12..1d1f5eb 100644
--- a/horizon/server/cluster.yml
+++ b/horizon/server/cluster.yml
@@ -2,6 +2,7 @@
 - service.keepalived.cluster.single
 - service.horizon.server.cluster
 - service.haproxy.proxy.single
+- system.apache.server.single
 - system.haproxy.proxy.listen.openstack.horizon
 - system.memcached.server.single
 parameters:
@@ -15,4 +16,7 @@
       plugin: {}
       session:
         engine: "cache"
-
+  apache:
+    server:
+      modules:
+        - wsgi