[RFE] limit the number of nodes that are fenced simultaniously

[ingvagabund]

In case a cluster is saturated we should restart only one node at a given time so the cluster has time to recover from the temporal lost of the node. It can take some time for all containers to get up and running again. Meantime, the cluster can start creating additional pods (just because RC, DS, etc. say so). Doing that for 3 nodes at the same time could degrade quality of services provided by the cluster.