Disable sniffing for elasticsearch output

The sniffing and template generation process will be enabled or disabled
when run along side data/ingest nodes. This will cut down on network IO
as the logstash output will use localhost to communicate to
elasticsearch whenever possible.

Change-Id: Ic289a2b8005cc76570420d74a2b46e2f1eccafbd
Signed-off-by: Kevin Carter <kevin.carter@rackspace.com>

elk_metrics_6x/templates/99-elasticsearch-output.conf.j2

@@ -1,8 +1,8 @@
 output {
   elasticsearch {
     hosts => {{ elasticsearch_data_hosts | shuffle(seed=inventory_hostname) | to_json }}
-    sniffing => true
-    manage_template => false
+    sniffing => {{ (not data_node | bool) | lower }}
+    manage_template => {{ (not data_node | bool) | lower }}
     index => "%{[@metadata][beat]}-%{[@metadata][version]}-%{+YYYY.MM.dd}"
   }
 }