@Override
    public String toString() {
      return varname;
    }
This is useful if you need the variable name for a LOG message or
{@link System#setProperty(String, String)}, beware however that you should only use this
with setProperty if you're going to create a configuration via
{@link MetastoreConf#newMetastoreConf()}.  If you are going to create it with HiveConf,
then use {@link #getHiveName()}.
@return metastore.* configuration key
standalone-metastore/metastore-common/src/main/java/org/apache/hadoop/hive/metastore/conf/MetastoreConf.java