[AS7-6539] fix messaging transformers

* revert the transformation of the CLUSTERED attribute to be compatible
  with legacy versions. On new version, writing to the attribute is
  ignored
  - the attribute is again stored in the configuration (but remains
    deprecated)
* add a model fixer to the transformation tests to remove the
  description of messaging path resources with default values that are
  always created since 7.2.x (AS7-5417)