[FIX] res.partner: avoid hiding `parent_id` and `child_ids` fields if they are set, irregardless of the rest of the `is_company` flag
[FIX] res.partner: avoid hiding `parent_id` and `child_ids` fields if they are set, irregardless of the rest of the `is_company` flag

This prevents hiding real data and also allows creating more
complex/flexible structures by setting the values of these
fields before or after setting is_company, to reach the
desired result.

akretion/openerp-server,akretion/openerp-server,akretion/openerp-server