Akka downing strategy, restart on quarantine/shutdown.

Down unreachable members if cluster membership is stable and majority
reachable.

Detect if this member has been quarantined, e.g. downed before
reconnect, and restart actor system so can rejoin cluster.

Detect if cluster has been shut down, e.g. downed after reconnect,
and restart.

This improves resilience in some cases where multiple members fail and a
strict subset of those attempt to rejoin.

community/common/src/main/java/org/neo4j/kernel/lifecycle/SafeLifecycle.java

@@ -180,7 +180,7 @@ public State state()
         return state;
     }
 
-    enum State
+    protected enum State
     {
         PRE,
         IDLE,