Unhard-coded 'message_queue:port:${_param:rabbitmq_port}'

Change-Id: I9c57a01b4e9f3b5cc03a7618ac8b7af1d227ab76
diff --git a/ceilometer/agent/single.yml b/ceilometer/agent/single.yml
index 0b0bbc3..cfcb855 100644
--- a/ceilometer/agent/single.yml
+++ b/ceilometer/agent/single.yml
@@ -1,7 +1,11 @@
 classes:
 - service.ceilometer.agent.single
 parameters:
+  _param:
+    openstack_rabbitmq_port: 5672
   ceilometer:
     agent:
+      message_queue:
+        port: ${_param:openstack_rabbitmq_port}
       identity:
         protocol: ${_param:internal_protocol}