portal_categories.getRelatedValueList(my_document,
base_category_list=["category_1", "category_2"]) should return any document
related through category_1 or through category_2.

Before this fix, only documents having this in categories match :
category_1/path_to/my_document
category_2/path_to/my_document

There was clearly a regression, since script Organisation_jumpToRelatedObjectList
was working fine for years (it pass many base_category to getRelatedValueList), and
it was not working any more.