Partial revert of commit 39d17c2580
of PR #4617, that broke translations by introducing a different
set of criterions for filtering translations in `_set_ids()` and
`_get_ids()`, adding the `module` column in `_set_ids`.
This meant `_get_ids` would see translations that `_set_ids`
would never update: the translation interface did not appear to
be working anymore as soon as a translation entry existed with
no `module` value.
This is likely for manual entries and for entries bootstrapped
by `translate_fields()`, as they do not belong to any module.
The situation described in PR #4617 probably requires an extra
fix in the translation import system instead.
5a41a3011a