Automatic merge from submit-queue
Don't require failureDomains in PodAffinityChecker
`failureDomains` are only used for `PreferredDuringScheduling` pod
anti-affinity, which is ignored by `PodAffinityChecker`.
This unnecessary requirement was making it hard to move
`PodAffinityChecker` to `GeneralPredicates` because that would require
passing `--failure-domains` to both `kubelet` and `kube-controller-manager`.
Automatic merge from submit-queue
Fix comment and optimize code
**What this PR does / why we need it**:
Fix comment and optimize code.
Thanks.
**Special notes for your reviewer**:
**Release note**:
```release-note
```
failureDomains are only used for PreferredDuringScheduling pod
anti-affinity, which is ignored by PodAffinityChecker.
This unnecessary requirement was making it hard to move
PodAffinityChecker to GeneralPredicates because that would require
passing --failure-domains to both kubelet and kube-controller-manager.