protected static String getDataDirectoryPath(Map<String, String> commandParameters) {
    return getCommandParameterValue(commandParameters, DATA_DIRECTORY);
  }
Given a (command parameter) Map, attempts to safely retrieve the "data_directory" property.

@param commandParameters a Map containing the dictionary of data to interrogate
@return a String indicating the data directory or null (if not found or set)
ambari-server/src/main/java/org/apache/ambari/server/serveraction/kerberos/KerberosServerAction.java