protected void updateLoad(final Map<ServerName, ServerAndLoad> map, final ServerName sn,
    final int diff) {
    ServerAndLoad sal = map.get(sn);
    if (sal == null) sal = new ServerAndLoad(sn, 0);
    sal = new ServerAndLoad(sn, sal.getLoad() + diff);
    map.put(sn, sal);
  }
This assumes the RegionPlan HSI instances are the same ones in the map, so actually no need to
even pass in the map, but I think it's clearer.
@return a list of all added {@link ServerAndLoad} values.
hbase-balancer/src/test/java/org/apache/hadoop/hbase/master/balancer/BalancerTestBase.java