[FIX] mrp: don't add missing consump warning line to backorder

Previous fix odoo/odoo#131279 missed marking component lines added in
from the consumption warning wizard as "additional". This made it so the
added line was also added into the backorder when it should NOT have
been (since the backorder should only be based on the original MO's
values).

Followup of task: 3456604

closes odoo/odoo#136019

Signed-off-by: Steve Van Essche <svs@odoo.com>