public String getOverlayOptionsAsQueryString() {
    return Joiner.on(";").withKeyValueSeparator("=").join(overlay);
  }
Get all overlay options as a query string.
This can be used in jdbc connection related tests where we want to pass
only the specific values which were set in this class.
common/src/test/org/apache/hadoop/hive/conf/HiveConfForTest.java