About failover

[Gaojinchao <ga...@huawei.com>]

version: Trunk.
When we startup a cluster, processDeadServers shouldn't be called,
otherwise we will create a lots of unuseful zk nodes.

As follows:
void joinCluster() throws IOException, KeeperException, InterruptedException {


    Map<ServerName,List<Pair<HRegionInfo,Result>>> deadServers =
      rebuildUserRegions();

//when startup the cluster,all regions are considered as dead ones.
//we will create a offline zk node for each region. But these nodes are cleared in function processRegionsInTransition
processDeadServers(deadServers);

    //Determine whether it is failover. If it is not , we will clean all the zk nodes.
    processRegionsInTransition(deadServers);
  }