[BUG] Error using picking.message_ids.search() to find the sub set messages for the given picking

Created by: zaoral

module: stock_picking_log_message_transfer

Make a POC of the next section of unit test

            picking = picking.message_ids.search([
                ('body', 'ilike', '%Picking transfered%')])

complete original code here

I presume that the search result involves all the mail.message in the system, and not the picking.message_ids sub set as it was planned to.

NOTE: This error was introduce in PR #785

HINT: Use filtered instead search will fix the error