[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

rql('SET X name "BoundaryConstraint" '
    'WHERE X is CWConstraintType, X name "BoundConstraint"')