Reconcile "reap" when no cluster leader

[armon]

If a member fails and is subsequently "reaped" from the Serf pool, this will trigger the node to be deregistered on the cluster leader. However, if there is no cluster leader, this event is lost. All other member events deal with this using a periodic reconciliation. However, after a reap, the node is no longer in the Serf pool, but exists in the catalog. The presence in the catalog must be reconciled with the absence in Serf and treated as a "reap" event. However, this is an extreme edge case, and also complex as there is no simple way to do this currently.