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`.
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.