private void useDummyTxnManagerTemporarily(HiveConf hiveConf) throws Exception {
    hiveConf.setVar(HiveConf.ConfVars.HIVE_TXN_MANAGER, "org.apache.hadoop.hive.ql.lockmgr.DummyTxnManager");
    txnMgr = SessionState.get().initTxnMgr(hiveConf);
    Assert.assertTrue(txnMgr instanceof DummyTxnManager);
  }
Temporarily set DummyTxnManager as the txn manager for the session.
HIVE-10632: we have to do this for every new query, because this jira introduced an AcidEventListener
in HiveMetaStore, which will instantiate a txn handler, but due to HIVE-12902, we have to call
TxnHandler.setConf and TxnHandler.checkQFileTestHack and TxnDbUtil.setConfValues, which will
set txn manager back to DbTxnManager.
ql/src/test/org/apache/hadoop/hive/ql/lockmgr/TestDbTxnManager2.java