Fetching galera status metrics in MySQL

These are useful for Percona Xtradb cluster.

closes #1437

CHANGELOG.md

@@ -34,6 +34,7 @@ should now look like:
 - [#1350](https://github.com/influxdata/telegraf/pull/1350): cgroup input plugin.
 - [#1369](https://github.com/influxdata/telegraf/pull/1369): Add input plugin for consuming metrics from NSQD.
 - [#1387](https://github.com/influxdata/telegraf/pull/1387): **Breaking Change** - Redis `role` tag renamed to `replication_role` to avoid global_tags override
+- [#1437](https://github.com/influxdata/telegraf/pull/1437): Fetching Galera status metrics in MySQL
 
 ### Bugfixes
 

plugins/inputs/mysql/mysql.go

@@ -306,6 +306,10 @@ var mappings = []*mapping{
 		onServer: "Threadpool_",
 		inExport: "threadpool_",
 	},
+	{
+		onServer: "wsrep_",
+		inExport: "wsrep_",
+	},
 }
 
 var (