make keystone authentication variable

Change-Id: I553e0b64b17a863f90fdd72d6a53ac5757757003
diff --git a/metadata/service/client/cluster.yml b/metadata/service/client/cluster.yml
index 05e608b..d5dadbb 100644
--- a/metadata/service/client/cluster.yml
+++ b/metadata/service/client/cluster.yml
@@ -3,6 +3,7 @@
 parameters:
   opencontrail:
     client:
+      version: 2.21
       identity:
         engine: keystone
         host: ${_param:cluster_vip_address}