private ServerName getServerFromFavoredNode(List<ServerName> servers, ServerName fn) {
    for (ServerName server : servers) {
      if (ServerName.isSameAddress(fn, server)) {
        return server;
      }
    }
    return null;
  }
Get the ServerName for the FavoredNode. Since FN's startcode is -1, we could want to get the
ServerName with the correct start code from the list of provided servers.
hbase-balancer/src/main/java/org/apache/hadoop/hbase/master/balancer/FavoredStochasticBalancer.java