@Override
    public void run() {
      if (waitForGroupTableOnline()) {
        LOG.info("GroupBasedLoadBalancer is now online");
      } else {
        LOG.warn("Quit without making region group table online");
      }
    }
Update cache of rsgroups. Caller must be synchronized on 'this'.
@param currentGroups Current list of Groups.
hbase-server/src/main/java/org/apache/hadoop/hbase/rsgroup/RSGroupInfoManagerImpl.java