Configure ceilometer coordination backend_url

Add ability to configure ceilometer coordination backend_url from
coordination_backend:redis pillar if enabled

Related-Prod: PROD-29126

Change-Id: I97acb85ae93300102d50dbbd9eb89597b6f1e666
diff --git a/tests/pillar/server_cluster.sls b/tests/pillar/server_cluster.sls
index be5f1bb..db6ce31 100644
--- a/tests/pillar/server_cluster.sls
+++ b/tests/pillar/server_cluster.sls
@@ -59,6 +59,19 @@
         enabled: true
         host: 127.0.0.4
         port: 8086
+    coordination_backend:
+      url: 'redis://127.0.0.1/test'
+      engine: redis
+      redis:
+        password: pswd
+        user: openstack
+        db: '0'
+        sentinel:
+          host: 127.0.0.1
+          master_name: master_1
+          fallback:
+            - host: 127.0.1.1
+            - host: 127.0.2.1
     notification:
       workers: 8
       batch_timeout: 10