simplify the self.assertEquals(int, getInventory(...........)) idiom

Introduce instead a simple getInventoryEquals, inspired by TestInventoryDocument
This allows transforming several linewrapped calls into plain one line calls,
for increased readability


git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@32246 20353a03-c40f-0410-a6d1-a30d3c3de9de