Fix metric buffer limit in internal plugin after reload

CHANGELOG.md

@@ -72,6 +72,7 @@
 ### Bugfixes
 
 - [#1896](https://github.com/influxdata/telegraf/issues/1896): Fix various mysql data type conversions.
+- [#3810](https://github.com/influxdata/telegraf/issues/3810): Fix metric buffer limit in internal plugin after reload.
 
 ## v1.5.3 [unreleased]
 

internal/models/running_output.go

@@ -87,7 +87,7 @@ func NewRunningOutput(
 			map[string]string{"output": name},
 		),
 	}
-	ro.BufferLimit.Incr(int64(ro.MetricBufferLimit))
+	ro.BufferLimit.Set(int64(ro.MetricBufferLimit))
 	return ro
 }