kubeadm: don't check if image exists before pulling

Removed image existence as kubeadm may miss
image tags if they're updated.

cmd/kubeadm/app/preflight/checks.go

@@ -833,14 +833,6 @@ func (ImagePullCheck) Name() string {
 // Check pulls images required by kubeadm. This is a mutating check
 func (ipc ImagePullCheck) Check() (warnings, errorList []error) {
 	for _, image := range ipc.imageList {
-		ret, err := ipc.runtime.ImageExists(image)
-		if ret && err == nil {
-			klog.V(1).Infof("image exists: %s", image)
-			continue
-		}
-		if err != nil {
-			errorList = append(errorList, errors.Wrapf(err, "failed to check if image %s exists", image))
-		}
 		klog.V(1).Infof("pulling %s", image)
 		if err := ipc.runtime.PullImage(image); err != nil {
 			errorList = append(errorList, errors.Wrapf(err, "failed to pull image %s", image))