Automatic merge from submit-queue (batch tested with PRs 51054, 51101, 50031, 51296, 51173) Add host mountpath to controller-manager for flexvolume dir Controller manager needs access to Flexvolume plugin when using attach-detach controller interface. This PR adds the host mount path for the default directory of flexvolume plugins Fixes https://github.com/kubernetes/kubeadm/issues/410