Update kubernetes dependency to 1.15.0.

Signed-off-by: Lantao Liu <lantaol@google.com>

vendor/k8s.io/kubernetes/pkg/util/bandwidth/utils.go

@@ -35,6 +35,7 @@ func validateBandwidthIsReasonable(rsrc *resource.Quantity) error {
 	return nil
 }
 
+// ExtractPodBandwidthResources extracts the ingress and egress from the given pod annotations
 func ExtractPodBandwidthResources(podAnnotations map[string]string) (ingress, egress *resource.Quantity, err error) {
 	if podAnnotations == nil {
 		return nil, nil, nil