getServicePIPNames returns duplicated PIP name for single-stack IPv4 services

[Liunardy]

What happened:

For a single-stack IPv4 service with a PIP name annotation, getServicePIPNames returns ["my-pip", "my-pip"], the same IPv4 PIP name twice.
This is because it iterates over both IPv4 and IPv6, and getServicePIPName(svc, true) falls through to return the IPv4 annotation value for a single-stack IPv4 service.

cloud-provider-azure/pkg/provider/azure_utils.go

Lines 379 to 403 in c3c63a9

	func getServicePIPName(service *v1.Service, isIPv6 bool) string {
	if service == nil {
	return ""
	}
	if !isServiceDualStack(service) {
	v4Enabled, v6Enabled := getIPFamiliesEnabled(service)
	if isIPv6 && v6Enabled && !v4Enabled {
	if name := service.Annotations[consts.ServiceAnnotationPIPNameDualStack[true]]; name != "" {
	return name
	}
	}
	return service.Annotations[consts.ServiceAnnotationPIPNameDualStack[false]]
	}
	return service.Annotations[consts.ServiceAnnotationPIPNameDualStack[isIPv6]]
	}
	func getServicePIPNames(service *v1.Service) []string {
	var ips []string
	for _, ipVersion := range []bool{IPVersionIPv4, IPVersionIPv6} {
	ips = append(ips, getServicePIPName(service, ipVersion))
	}
	return ips
	}

The duplicate causes redundant PIP lookups

cloud-provider-azure/pkg/provider/azure_loadbalancer.go

Lines 4379 to 4391 in c3c63a9

	pipNames = getServicePIPNames(service)
	for _, pipName := range pipNames {
	if pipName != "" {
	pip, err := az.findMatchedPIP(ctx, "", pipName, pipResourceGroup)
	if err != nil {
	klog.Warningf("serviceOwnsFrontendIP: unexpected error when finding match public IP of the service %s with name %s: %v", service.Name, pipName, err)
	return false, isPrimaryService, nil
	}
	if publicIPOwnsFrontendIP(service, fip, pip) {
	return true, isPrimaryService, pip.Properties.PublicIPAddressVersion
	}
	}
	}

What you expected to happen:

getServicePIPNames should not return duplicates for a single-stack IPv4 service.