AddNode just adds a node to the cluster but does NOT perform rebalance.

AddNodeAndRebalance adds a node to the cluster and then does a rebalance.

RemoveNode performs a rebalance out (ejection) of the specified node.

RemoveNodes performs a rebalance out (ejection) of the specified node.

This function checks if servers are active on all the "nodes" In cases where the rebalance tests are run without required number of servers in cluster_run, this validation makes sure that all the tests are considered PASS.