@Override
        public String toString() {
            return "move " +
                   ( isEmpty() ? "none" : (node + " from " + fromHost.hostname() + " to " + toHost.hostname()));
        }
Returns true only if this operation changes the state of the preferToRetire flag
node-repository/src/main/java/com/yahoo/vespa/hosted/provision/maintenance/MaintenanceDeployment.java