public static void expandHiveConfParams(HiveConf hiveConf) {
    Iterator<Map.Entry<String, String>> iter = hiveConf.iterator();
    while (iter.hasNext()) {
      String key = iter.next().getKey();
      hiveConf.set(key, hiveConf.get(key));
    }
  }
Do the variable expansion by calling "set" on each variable.
When MR jobs are run, under some circumstances they fail because
the variable expansion fails after changes in Hadoop to prevent
variable expansion for JobHistoryServer. So expanding them ahead
so that variables like {test.tmp.dir} get expanded.
@param hiveConf
itests/hive-unit/src/test/java/org/apache/hadoop/hive/UtilsForTest.java