tests: Replaces images used with agnhost (part 1)

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:

- fakegitserver
- hostexec
- liveness
- logs-generator
- no-snat-test
- no-snat-test-proxy
- port-forward-tester

test/e2e/storage/empty_dir_wrapper.go

@@ -221,7 +221,8 @@ func createGitServer(f *framework.Framework) (gitURL string, gitRepo string, cle
 			Containers: []v1.Container{
 				{
 					Name:            "git-repo",
-					Image:           imageutils.GetE2EImage(imageutils.Fakegitserver),
+					Image:           imageutils.GetE2EImage(imageutils.Agnhost),
+					Args:            []string{"fake-gitserver"},
 					ImagePullPolicy: "IfNotPresent",
 					Ports: []v1.ContainerPort{
 						{ContainerPort: int32(containerPort)},