We do this because they will be recreated immediately by the
DaemonSet Controller. In addition, we also require a specific flag
(--ignore-daemonsets) when there are DaemonSet pods on the node.
It cordons (marks unschedulable) the given node, and then deletes every
pod on it, optionally using a grace period. It will not delete pods
managed by neither a ReplicationController nor a DaemonSet without the
use of --force.
Also add cordon/uncordon, which just toggle node schedulability.