This fixes #20170313-5DDBB0 (partially, but I think it's enough)

 ... update. It's not enough see
https://nexedi.erp5.net/test_result_module/20170313-4DA9CA7B/59
this only works for payable / receiveable accounts.
In reality, the number of mirror_section_uid is potentially very large
(think role/client with thousands of individual customer), so that
approach to use getInventoryList(group_by_mirror_section=True) to
collect all mirror section uids seems wrong to me now.