dataclients/kubernetes: add failing testcase for named service target port

[AlexanderYastrebov]

For #2565

[AlexanderYastrebov]

Here service uses named target port which could only be resolved by reading pod definition.

Endpoints logic has a special condition for a single port:

skipper/dataclients/kubernetes/ingressdefinitions.go

Lines 91 to 99 in 52ef4ef

	func (ep endpoint) targetsByServicePort(protocol string, servicePort *servicePort) []string {
	for _, s := range ep.Subsets {
	// If only one port exists in the endpoint, use it
	if len(s.Ports) == 1 {
	return formatEndpointsForSubsetAddresses(s.Addresses, s.Ports[0], protocol)
	}
	// Otherwise match port by name
	for _, p := range s.Ports {

[AlexanderYastrebov]

Pushed to the #2565