tests: Replaces images used with agnhost (part 3)

Quite a few images are only used a few times in a few tests. Thus,
the images are being centralized into the agnhost image, reducing
the number of images that have to be pulled and used.

This PR replaces the usage of the following images with agnhost:

- audit-proxy
- crd-conversion-webhook
- entrypoint-tester
- inclusterclient
- iperf
- porter
- serve-hostname

test/e2e_node/image_list.go

@@ -44,13 +44,13 @@ const (
 // NodeImageWhiteList is a list of images used in node e2e test. These images will be prepulled
 // before test running so that the image pulling won't fail in actual test.
 var NodeImageWhiteList = sets.NewString(
+	imageutils.GetE2EImage(imageutils.Agnhost),
 	"google/cadvisor:latest",
 	"k8s.gcr.io/stress:v1",
 	busyboxImage,
 	"k8s.gcr.io/busybox@sha256:4bdd623e848417d96127e16037743f0cd8b528c026e9175e22a84f639eca58ff",
 	imageutils.GetE2EImage(imageutils.Nginx),
 	imageutils.GetE2EImage(imageutils.Perl),
-	imageutils.GetE2EImage(imageutils.ServeHostname),
 	imageutils.GetE2EImage(imageutils.Nonewprivs),
 	imageutils.GetPauseImageName(),
 	gpu.GetGPUDevicePluginImage(),