Merge pull request #52597 from smarterclayton/roundtrip_options

Automatic merge from submit-queue (batch tested with PRs 52485, 52443, 52597, 52450, 51971). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>..

Some kubelet flags do not accept their default values

Correct the flags and add a round trip test that ensure these do not
break again in the future.

@deads2k as observed when we tried to turn flags into args.

pkg/util/taints/taints.go

@@ -76,6 +76,10 @@ type taintsVar struct {
 }
 
 func (t taintsVar) Set(s string) error {
+	if len(s) == 0 {
+		*t.ptr = nil
+		return nil
+	}
 	sts := strings.Split(s, ",")
 	var taints []api.Taint
 	for _, st := range sts {
@@ -91,7 +95,7 @@ func (t taintsVar) Set(s string) error {
 
 func (t taintsVar) String() string {
 	if len(*t.ptr) == 0 {
-		return "<nil>"
+		return ""
 	}
 	var taints []string
 	for _, taint := range *t.ptr {