private List<Transfer> getAllowedTransfers(Cluster cluster, String configType, List<Transfer> transfers){
    List<Transfer> allowedTransfers = new ArrayList<>();
    for (Transfer transfer : transfers) {
      String key;
      if(transfer.operation == TransferOperation.DELETE) {
        key = transfer.deleteKey;
      } else {
        key = transfer.fromKey;
      }

      if(isOperationAllowed(cluster, configType, key, transfer)) {
        allowedTransfers.add(transfer);
      }
    }

    return allowedTransfers;
  }
Finds the values that should be preserved during a delete. This includes:
<ul>
<li>Properties that existed on the stack but were changed to a different
value</li>
<li>Properties that do not exist on the stack</li>
</ul>

@param clusterName
         the cluster name
@param config
         the config with the tag to find conflicts
@return the list of changed property keys
@throws AmbariException
ambari-server/src/main/java/org/apache/ambari/server/serveraction/upgrades/ConfigureAction.java