e2e: grab controller and scheduler metrics via port forwarding

The previous approach with grabbing via a nginx proxy had some
drawbacks:
- it did not work when the pods only listened on localhost (as
  configured by kubeadm) and the proxy got deployed on a different
  node
- starting the proxy raced with starting the pods, causing
  sporadic test failures because the proxy was not set up
  properly unless it saw all pods when starting the e2e.test
- the proxy was always started, whether it is needed or not
- the proxy was left running after a test and then the next
  test run triggered potentially confusing messages when
  it failed to create objects for the proxy

The new approach is similar to "kubectl port-forward" + "kubectl get
--raw". It uses the port forwarding feature to establish a TCP
connection via a custom dialer, then lets client-go handle TLS and
credentials.

Somehow verifying the server certificate did not work. As this
shouldn't be a big concern for E2E testing, certificate checking gets
disabled on the client side instead of investigating this further.

test/e2e/framework/framework.go

@@ -296,7 +296,7 @@ func (f *Framework) BeforeEach() {
 
 	gatherMetricsAfterTest := TestContext.GatherMetricsAfterTest == "true" || TestContext.GatherMetricsAfterTest == "master"
 	if gatherMetricsAfterTest && TestContext.IncludeClusterAutoscalerMetrics {
-		grabber, err := e2emetrics.NewMetricsGrabber(f.ClientSet, f.KubemarkExternalClusterClientSet, !ProviderIs("kubemark"), false, false, false, TestContext.IncludeClusterAutoscalerMetrics, false)
+		grabber, err := e2emetrics.NewMetricsGrabber(f.ClientSet, f.KubemarkExternalClusterClientSet, f.ClientConfig(), !ProviderIs("kubemark"), false, false, false, TestContext.IncludeClusterAutoscalerMetrics, false)
 		if err != nil {
 			Logf("Failed to create MetricsGrabber (skipping ClusterAutoscaler metrics gathering before test): %v", err)
 		} else {
@@ -449,7 +449,7 @@ func (f *Framework) AfterEach() {
 		ginkgo.By("Gathering metrics")
 		// Grab apiserver, scheduler, controller-manager metrics and (optionally) nodes' kubelet metrics.
 		grabMetricsFromKubelets := TestContext.GatherMetricsAfterTest != "master" && !ProviderIs("kubemark")
-		grabber, err := e2emetrics.NewMetricsGrabber(f.ClientSet, f.KubemarkExternalClusterClientSet, grabMetricsFromKubelets, true, true, true, TestContext.IncludeClusterAutoscalerMetrics, false)
+		grabber, err := e2emetrics.NewMetricsGrabber(f.ClientSet, f.KubemarkExternalClusterClientSet, f.ClientConfig(), grabMetricsFromKubelets, true, true, true, TestContext.IncludeClusterAutoscalerMetrics, false)
 		if err != nil {
 			Logf("Failed to create MetricsGrabber (skipping metrics gathering): %v", err)
 		} else {