This implements Bulk volume polling using ideas presented by
justin in https://github.com/kubernetes/kubernetes/pull/39564
But it changes the implementation to use an interface
and doesn't affect other implementations.
The kube-controller-manager has two command line arguments (--pv-recycler-pod-template-filepath-hostpath and --pv-recycler-pod-template-filepath-nfs) that specify a recycle pod template. The recycle pod template may not contain the volume that shall be recycled.
A check is added to make sure that the recycle pod template contains at least a volume.