Currently we allow selection of the rollback algorithm to use by means of the 'rollbackMethod' server parameter. We should only allow the 'rollbackViaRefetchNoUUID' to be used when a node is in FCV=3.4, and only allow the rollbackViaRefetch' algorithm when the node is in FCV=3.6. This may involve removing the 'rollbackMethod' server parameter, since the algorithm will be bound to FCV, instead of being user selectable.