public String removeProperty(String configType, String propertyName) {
    String previousValue = null;
    if (properties.containsKey(configType)) {
      previousValue = properties.get(configType).remove(propertyName);
    }

    if (parentConfiguration != null) {
      String parentPreviousValue =  parentConfiguration.removeProperty(configType, propertyName);
      if (previousValue == null) {
        previousValue = parentPreviousValue;
      }
    }
    return previousValue;
  }
Remove a property from the configuration hierarchy.
All occurrences of the property are removed from the config hierarchy such that
a subsequent call to getPropertyValue() for the removed property will return null.

@param configType    configuration type
@param propertyName  property name

@return the previous value of the removed property or null if it didn't exist in the
        configuration hierarchy
ambari-server/src/main/java/org/apache/ambari/server/topology/Configuration.java