added url to the heartbeat check

roles/os_zabbix/vars/template_heartbeat.yml

@@ -10,3 +10,4 @@ g_template_heartbeat:
   - description: 'Heartbeat.ping has failed on {HOST.NAME}'
     expression: '{Template Heartbeat:heartbeat.ping.nodata(20m)}=1'
     priority: avg
+    url: 'https://github.com/openshift/ops-sop/blob/master/V3/Alerts/check_node_heartbeat.asciidoc'