Automatic merge from submit-queue (batch tested with PRs 49850, 47782, 50595, 50730, 51341)

Fix benchmarks to really test reverse order of the keys

**What this PR does / why we need it**:
This PR modifies the code to do what comments says -- reverse the order of keys. It also fixes the logic that was wrong and didn't allow stale data.

**Special notes for your reviewer**:
This change resolves the following review comments:
- https://github.com/kubernetes/kubernetes/pull/41939#discussion_r117068104
- https://github.com/kubernetes/kubernetes/pull/46916#discussion_r122763350
- https://github.com/kubernetes/kubernetes/pull/46916#discussion_r122764000

**Release note**:
```release-note
NONE
```

PTAL @smarterclayton