Automatic merge from submit-queue

Guarantee watch before action in e2e event observer helper function.

**What this PR does / why we need it**:

Adds a missing synchronization barrier to an e2e event observation helper function.

- This change should guarantee that in observeEventAfterAction,
  the action is only executed after the informer begins watching
  the event stream.

**Release note**:

```release-note
NONE
```

cc @kubernetes/sig-scheduling-pr-reviews @bsalamat