@Override
  public void onConfigurationChange(Configuration conf) {
    loadConf(conf);
  }
Perform the major balance operation for cluster, will invoke
{@link #balanceTable(TableName, Map)} to do actual balance.
<p/>
THIs method is marked as final which means you should not override this method. See the javadoc
for {@link #balanceTable(TableName, Map)} for more details.
@param loadOfAllTable region load of servers for all table
@return a list of regions to be moved, including source and destination, or null if cluster is
        already balanced
@see #balanceTable(TableName, Map)
hbase-balancer/src/main/java/org/apache/hadoop/hbase/master/balancer/BaseLoadBalancer.java