Don't delete affinity when endpoints are empty

This only affects the userspace kube-proxy.

pkg/proxy/userspace/loadbalancer.go

@@ -29,5 +29,6 @@ type LoadBalancer interface {
 	// service-port and source address.
 	NextEndpoint(service proxy.ServicePortName, srcAddr net.Addr) (string, error)
 	NewService(service proxy.ServicePortName, sessionAffinityType api.ServiceAffinity, stickyMaxAgeMinutes int) error
+	DeleteService(service proxy.ServicePortName)
 	CleanupStaleStickySessions(service proxy.ServicePortName)
 }