[entity] more tweaks for entity attribute cache handling on cw_set/cw_create to fix test regression * when an attribute is listed in dont-cache-attrs, purge any previous value * test value is actually modified in EditedEntity.__setitem__ before adding attribute to dont-cache-attrs

Latest changes 
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* table of `all latest changes`_

Links below is providing useful RQL query example.

.. _all latest changes: view?rql=Any+M%2CX+WHERE+X+modification_date+M+ORDERBY+M+DESC+LIMIT+30