@After
  public void cleanupTestTable() throws Exception {
    UTIL.getAdmin().disableTable(primaryTable);
    UTIL.getAdmin().deleteTable(primaryTable);

    UTIL.getAdmin().disableTable(otherTable);
    UTIL.getAdmin().deleteTable(otherTable);

  }
@return a pool that has one thread only at every time. A second action added to the pool (
        running concurrently), will cause an exception.
hbase-server/src/test/java/org/apache/hadoop/hbase/coprocessor/TestOpenTableInCoprocessor.java