Validate Node IPs; clean up validation code

pkg/api/helpers.go

@@ -113,3 +113,20 @@ var standardFinalizers = util.NewStringSet(
 func IsStandardFinalizerName(str string) bool {
 	return standardFinalizers.Has(str)
 }
+
+// AddToNodeAddresses appends the NodeAddresses to the passed-by-pointer slice,
+// only if they do not already exist
+func AddToNodeAddresses(addresses *[]NodeAddress, addAddresses ...NodeAddress) {
+	for _, add := range addAddresses {
+		exists := false
+		for _, existing := range *addresses {
+			if existing.Address == add.Address && existing.Type == add.Type {
+				exists = true
+				break
+			}
+		}
+		if !exists {
+			*addresses = append(*addresses, add)
+		}
+	}
+}