Evict any already-running pods that do not tolerate the taint.
Currently enforced by NodeController.
NoSchedule
Do not allow new pods to schedule onto the node unless they tolerate the
taint, but allow all pods submitted to Kubelet without going through the
scheduler to start, and allow all already-running pods to continue
running. Enforced by the scheduler.
PreferNoSchedule
Like TaintEffectNoSchedule, but the scheduler tries not to schedule
new pods onto the node, rather than prohibiting new pods from scheduling
onto the node entirely. Enforced by the scheduler.
