Rolling upgrades that cross compatibility boundaries must be preformed in multiple steps. For example, to perform a rolling update from Heartbeat 2.0.1 to Pacemaker 0.6.6 one must:
Perform a rolling upgrade from Heartbeat 2.0.1 to Heartbeat 2.0.4
Perform a rolling upgrade from Heartbeat 2.0.4 to Heartbeat 2.1.3
Perform a rolling upgrade from Heartbeat 2.1.3 to Pacemaker 0.6.6
