Enable notifications for top-level clusters

This commit uses "alerting: enabled_with_notification" for the
contrail-control and contrail-compute alarm clusters.

Change-Id: Ic7bde42a60efb0d91085668f97d4da7d95f3a3d5
diff --git a/opencontrail/meta/heka.yml b/opencontrail/meta/heka.yml
index 0b04c0a..987eaa0 100644
--- a/opencontrail/meta/heka.yml
+++ b/opencontrail/meta/heka.yml
@@ -647,7 +647,7 @@
         nagios_host: 01-service-clusters
     contrail_control:
       policy: highest_severity
-      alerting: enabled
+      alerting: enabled_with_notification
       match:
         service: contrail-control
       members:
@@ -686,7 +686,7 @@
         nagios_host: 01-service-clusters
     contrail_compute:
       policy: highest_severity
-      alerting: enabled
+      alerting: enabled_with_notification
       match:
         service: contrail-compute
       members: