Fix review findings

Author: sbueringer

bootstrap/kubeadm/api/v1beta1/kubeadm_types.go

@@ -451,7 +451,7 @@ type LocalEtcd struct {
 type ExternalEtcd struct {
 	// endpoints of etcd members. Required for ExternalEtcd.
 	// +kubebuilder:validation:MaxItems=50
-	// +kubebuilder:validation:items:MaxLength=256
+	// +kubebuilder:validation:items:MaxLength=512
 	Endpoints []string `json:"endpoints"`
 
 	// caFile is an SSL Certificate Authority file used to secure etcd communication.