Fix designate pools update

designate-manage pools update command should be run
only on pools.yaml file changes

Change-Id: I8a12fb7d31e75932ad0c8a9997313fe820eccede
Related-Prod: https://mirantis.jira.com/browse/OSCORE-232
diff --git a/designate/server.sls b/designate/server.sls
index 246887b..82be0ad 100644
--- a/designate/server.sls
+++ b/designate/server.sls
@@ -79,8 +79,9 @@
   cmd.run:
     - name: designate-manage pool update
     - require:
-      - file: /etc/designate/pools.yaml
       - service: designate_server_services
+    - onchanges:
+      - file: /etc/designate/pools.yaml
 {%- endif %}
 {%- endif %}
 {%- endif %}