kubelet: Move TestPortForwardNoSuchContainer() to dockertools package.

Also refactor TestPortForward() to be neutral to container runtime.

pkg/kubelet/container/runtime.go

@@ -19,6 +19,7 @@ package container
 import (
 	"fmt"
 	"io"
+	"reflect"
 	"strings"
 
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/api"
@@ -282,6 +283,11 @@ func (p *Pod) FindContainerByName(containerName string) *Container {
 	return nil
 }
 
+// IsEmpty returns true if the pod is empty.
+func (p *Pod) IsEmpty() bool {
+	return reflect.DeepEqual(p, &Pod{})
+}
+
 // GetPodFullName returns a name that uniquely identifies a pod.
 func GetPodFullName(pod *api.Pod) string {
 	// Use underscore as the delimiter because it is not allowed in pod name