Remove unnecessary select statement (#692)

* Remove unnecessary select statement

* Remove unnecessary if-statement

node_exporter_test.go

@@ -129,14 +129,9 @@ func runCommandAndTests(cmd *exec.Cmd, address string, fn func(pid int) error) e
 		errc <- fn(pid)
 	}(cmd.Process.Pid)
 
-	select {
+	err := <-errc
-	case err := <-errc:
 	if cmd.Process != nil {
 		cmd.Process.Kill()
 	}
-		if err != nil {
 	return err
 }
-	}
-	return nil
-}