Add lookup metadata_password param

Change-Id: Idd6271acf633ac7172af05a354628e8056eece12
diff --git a/nova/control/cluster.yml b/nova/control/cluster.yml
index 545a432..1bcc8b9 100644
--- a/nova/control/cluster.yml
+++ b/nova/control/cluster.yml
@@ -71,4 +71,4 @@
         mtu: 1500
         tenant: service
       metadata:
-        password: metadataPass
+        password: ${_param:metadata_password}