public UpgradeActionOperations addConfigurationChange(ConfigurationChanges configurationChanges) {
    if (null == m_configurationChanges) {
      m_configurationChanges = new ArrayList<>();
    }

    m_configurationChanges.add(configurationChanges);
    return this;
  }
Adds a single configuration change to the operations which should be
performed. This might be more useful thank the bulk methods, such as
{@link #setConfigurationChanges(List)}.

@param configurationChanges
         the configuration changes to make.
@return an instance of the {@link UpgradeActionOperations} with the value
        set.
ambari-server-spi/src/main/java/org/apache/ambari/spi/upgrade/UpgradeActionOperations.java