influxdb output: write consistency parameter

closes #1249

etc/telegraf.conf

@@ -75,12 +75,15 @@
   urls = ["http://localhost:8086"] # required
   ## The target database for metrics (telegraf will create it if not exists).
   database = "telegraf" # required
-  ## Retention policy to write to.
-  retention_policy = "default"
   ## Precision of writes, valid values are "ns", "us" (or "µs"), "ms", "s", "m", "h".
   ## note: using "s" precision greatly improves InfluxDB compression.
   precision = "s"
 
+  ## Retention policy to write to.
+  retention_policy = "default"
+  ## Write consistency (clusters only), can be: "any", "one", "quorom", "all"
+  write_consistency = "any"
+
   ## Write timeout (for the InfluxDB client), formatted as a string.
   ## If not provided, will default to 5s. 0s means no timeout (not recommended).
   timeout = "5s"