public static void closeRegion(HBaseTestingUtil HTU, HRegionServer rs, RegionInfo hri)
    throws Exception {
    AdminProtos.CloseRegionRequest crr =
      ProtobufUtil.buildCloseRegionRequest(rs.getServerName(), hri.getRegionName());
    AdminProtos.CloseRegionResponse responseClose = rs.getRpcServices().closeRegion(null, crr);
    Assert.assertTrue(responseClose.getClosed());
    checkRegionIsClosed(HTU, rs, hri);
  }
Flush the given region in the mini cluster. Since no master, we cannot use HBaseAdmin.flush()
hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/TestRegionServerNoMaster.java