Add ability to limit node stats in elasticsearch input (#3304)

plugins/inputs/elasticsearch/README.md

@@ -33,6 +33,11 @@ or [cluster-stats](https://www.elastic.co/guide/en/elasticsearch/reference/curre
   ## Master node.
   cluster_stats = false
 
+  ## node_stats is a list of sub-stats that you want to have gathered. Valid options
+  ## are "indices", "os", "process", "jvm", "thread_pool", "fs", "transport", "http",
+  ## "breakers". Per default, all stats are gathered.
+  # node_stats = ["jvm", "http"]
+
   ## Optional SSL Config
   # ssl_ca = "/etc/telegraf/ca.pem"
   # ssl_cert = "/etc/telegraf/cert.pem"