Automatic merge from submit-queue

[e2e density test] Fix unnecessary Delete RC requests when not running latency test

As the following code block
https://github.com/kubernetes/kubernetes/blob/master/test/e2e/density.go#L666-L670
shows, after running each density test case, it will attempt to delete "additional replication controllers" even though there is **no additional replication controller**.

When we are not running latency test, API Server will return "404 error code". So, I propose to move the above code block inside thedetermine statementsif `itArg.runLatencyTest{ }` , looks like:

```
if itArg.runLatencyTest {
  ...
  for i := 1; i <= nodeCount; i++ {
    name := additionalPodsPrefix + "-" + strconv.Itoa(i)
    c.ReplicationControllers(ns).Delete(name, nil)
  }
}
```
In this way, removing RC will be executed only if we set `itArg.runLatencyTest` to be `true`. It can avoid post some necessary requests to API Server.

Issuse is #30977