Automatic merge from submit-queue

Avoid unnecessary memory allocations

Low-hanging fruits in saving memory allocations. During our 5000-node kubemark runs I've see this:

ControllerManager:
- 40.17% k8s.io/kubernetes/pkg/util/system.IsMasterNode
- 19.04% k8s.io/kubernetes/pkg/controller.(*PodControllerRefManager).Classify

Scheduler:
- 42.74% k8s.io/kubernetes/plugin/pkg/scheduler/algrorithm/predicates.(*MaxPDVolumeCountChecker).filterVolumes

This PR is eliminating all of those.