@Override
    public Result preIncrement(final ObserverContext<? extends RegionCoprocessorEnvironment> e,
      final Increment increment) throws IOException {
      Threads.sleep(SLEEP_TIME);
      return null;
    }
This class is for testing HBaseConnectionManager ServerBusyException. Be careful adding to this
class. It sets a low HBASE_CLIENT_PERSERVER_REQUESTS_THRESHOLD
hbase-server/src/test/java/org/apache/hadoop/hbase/client/TestServerBusyException.java