improve iptables-restore implementation #27559

- improve restoreInternal implementation in iptables
- add SetStdin and SetStdout functions to Cmd interface
- modify kubelet/prober and some tests in order to work with Cmd interface

pkg/probe/exec/exec_test.go

@@ -18,6 +18,7 @@ package exec
 
 import (
 	"fmt"
+	"io"
 	"testing"
 
 	"k8s.io/kubernetes/pkg/probe"
@@ -39,6 +40,10 @@ func (f *FakeCmd) Output() ([]byte, error) {
 
 func (f *FakeCmd) SetDir(dir string) {}
 
+func (f *FakeCmd) SetStdin(in io.Reader) {}
+
+func (f *FakeCmd) SetStdout(out io.Writer) {}
+
 type fakeExitError struct {
 	exited     bool
 	statusCode int