@AfterClass
  public static void tearDownDb() {
    rule.after();
  }
Test class to run DbTxnManager tests against different dbms types.
Example: mvn test -Dtest=ITestDbTxnManager -Dtest.metastore.db=postgres
ql/src/test/org/apache/hadoop/hive/ql/lockmgr/ITestDbTxnManager.java