Generate random keystone users

Change-Id: I8dbd07b10d29b43d1c35fa76bcaa0f0efb32beda
Related-Prod: PROD-29868
diff --git a/sahara/server/single.yml b/sahara/server/single.yml
index fcb26c9..3b63c44 100644
--- a/sahara/server/single.yml
+++ b/sahara/server/single.yml
@@ -14,13 +14,13 @@
         host: ${_param:openstack_database_address}
         port: 3306
         name: sahara
-        user: sahara
+        user: ${_param:mysql_sahara_username}
         password: ${_param:mysql_sahara_password}
       identity:
         engine: keystone
         host: ${_param:openstack_control_address}
         port: 35357
-        user: sahara
+        user: ${_param:keystone_sahara_username}
         password: ${_param:keystone_sahara_password}
         tenant: service
       message_queue: