Use variadic disk.IOCounters() function

plugins/inputs/system/ps.go

@@ -121,7 +121,7 @@ func (s *systemPS) NetConnections() ([]net.ConnectionStat, error) {
 }
 
 func (s *systemPS) DiskIO(names []string) (map[string]disk.IOCountersStat, error) {
-	m, err := disk.IOCountersForNames(names)
+	m, err := disk.IOCounters(names...)
 	if err == internal.NotImplementedError {
 		return nil, nil
 	}