e2e: simplify test cleanup

ginkgo.DeferCleanup has multiple advantages:
- The cleanup operation can get registered if and only if needed.
- No need to return a cleanup function that the caller must invoke.
- Automatically determines whether a context is needed, which will
  simplify the introduction of context parameters.
- Ginkgo's timeline shows when it executes the cleanup operation.

test/e2e/apps/ttl_after_finished.go

@@ -78,7 +78,7 @@ func testFinishedJob(f *framework.Framework) {
 	job := e2ejob.NewTestJob("randomlySucceedOrFail", "rand-non-local", v1.RestartPolicyNever, parallelism, completions, nil, backoffLimit)
 	job.Spec.TTLSecondsAfterFinished = &ttl
 	job.ObjectMeta.Finalizers = []string{dummyFinalizer}
-	defer cleanupJob(f, job)
+	ginkgo.DeferCleanup(cleanupJob, f, job)
 
 	framework.Logf("Create a Job %s/%s with TTL", ns, job.Name)
 	job, err := e2ejob.CreateJob(c, ns, job)