Revert "Kubelet: Use RepoDigest for ImageID when available"

pkg/kubelet/dockertools/docker_manager_test.go

@@ -151,9 +151,6 @@ func createTestDockerManager(fakeHTTPClient *fakeHTTP, fakeDocker *FakeDockerCli
 		fakeHTTPClient,
 		flowcontrol.NewBackOff(time.Second, 300*time.Second))
 
-	// default this to an empty result, so that we never have a nil non-error response from InspectImage
-	fakeDocker.Image = &dockertypes.ImageInspect{}
-
 	return dockerManager, fakeDocker
 }