Kubelet: recreate mirror pod if the static pod changes

If a static pod changes, delete the corresponding mirror pod. When kubelet
could not see mirror pod from the API server update, it'd attemp to create a
new mirror pod with up-to-date specs.

pkg/kubelet/mirror_client_test.go

@@ -34,7 +34,7 @@ type fakeMirrorClient struct {
 	deleteCounts map[string]int
 }
 
-func (self *fakeMirrorClient) CreateMirrorPod(pod api.Pod, _ string) error {
+func (self *fakeMirrorClient) CreateMirrorPod(pod api.Pod) error {
 	self.mirrorPodLock.Lock()
 	defer self.mirrorPodLock.Unlock()
 	podFullName := kubecontainer.GetPodFullName(&pod)