synchronized void cleanAllPreviousInstances(final ServerName newServerName) {
    Iterator<ServerName> it = deadServers.keySet().iterator();
    while (it.hasNext()) {
      cleanOldServerName(newServerName, it);
    }
  }
Handles restart of a server. The new server instance has a different start code. The new start
code should be greater than the old one. We don't check that here. Removes the old server from
deadserver list.
@param newServerName Servername as either <code>host:port</code> or
                     <code>host,port,startcode</code>.
@return true if this server was dead before and coming back alive again
hbase-server/src/main/java/org/apache/hadoop/hbase/master/DeadServer.java