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
355f576c0b