Generate random keystone users

Change-Id: I8dbd07b10d29b43d1c35fa76bcaa0f0efb32beda
Related-Prod: PROD-29868
diff --git a/ceilometer/agent/cluster.yml b/ceilometer/agent/cluster.yml
index 6bb4e71..c24adf7 100644
--- a/ceilometer/agent/cluster.yml
+++ b/ceilometer/agent/cluster.yml
@@ -17,7 +17,7 @@
         host: ${_param:keystone_service_host}
         port: 35357
         tenant: service
-        user: ceilometer
+        user: ${_param:keystone_ceilometer_username}
         password: ${_param:keystone_ceilometer_password}
         region: ${_param:openstack_region}
         protocol: ${_param:cluster_internal_protocol}