Considere zookeeper's state as a tags (#1417)

This change will send the state of zookeeper (leader|follower) as a tag
and not a metrics
That way it will be easier to search for filter per state

plugins/inputs/zookeeper/README.md

@@ -32,7 +32,7 @@ echo mntr | nc localhost 2181
 
 Meta:
 - units: int64
-- tags: `server=<hostname> port=<port>`
+- tags: `server=<hostname> port=<port> state=<leader|follower>`
 
 Measurement names:
 - zookeeper_avg_latency
@@ -55,8 +55,12 @@ Measurement names:
 
 Meta:
 - units: string
-- tags: `server=<hostname> port=<port>`
+- tags: `server=<hostname> port=<port> state=<leader|follower>`
 
 Measurement names:
 - zookeeper_version
-- zookeeper_server_state
+
+### Tags:
+
+- All measurements have the following tags:
+	- 

plugins/inputs/zookeeper/zookeeper.go

@@ -55,6 +55,7 @@ func (z *Zookeeper) Gather(acc telegraf.Accumulator) error {
 }
 
 func (z *Zookeeper) gatherServer(address string, acc telegraf.Accumulator) error {
+	var zookeeper_state string
 	_, _, err := net.SplitHostPort(address)
 	if err != nil {
 		address = address + ":2181"
@@ -78,7 +79,6 @@ func (z *Zookeeper) gatherServer(address string, acc telegraf.Accumulator) error
 	if len(service) != 2 {
 		return fmt.Errorf("Invalid service address: %s", address)
 	}
-	tags := map[string]string{"server": service[0], "port": service[1]}
 
 	fields := make(map[string]interface{})
 	for scanner.Scan() {
@@ -92,6 +92,9 @@ func (z *Zookeeper) gatherServer(address string, acc telegraf.Accumulator) error
 		}
 
 		measurement := strings.TrimPrefix(parts[1], "zk_")
+		if measurement == "server_state" {
+			zookeeper_state = parts[2]
+		} else {
 			sValue := string(parts[2])
 
 			iVal, err := strconv.ParseInt(sValue, 10, 64)
@@ -101,6 +104,12 @@ func (z *Zookeeper) gatherServer(address string, acc telegraf.Accumulator) error
 				fields[measurement] = sValue
 			}
 		}
+	}
+	tags := map[string]string{
+		"server": service[0],
+		"port":   service[1],
+		"state":  zookeeper_state,
+	}
 	acc.AddFields("zookeeper", fields, tags)
 
 	return nil