Have an MX database set up
Activate multicurrency (MXN and USD)
Have several rate for USD
- yesterday 0.047939098170
- today 0.048486729180
Make an invoice, dated yesterday for USD 116, tax 16% (cash basis)
Create a received payment dated today, for USD 116
Reconcile invoice and payment

Jounal items will be created for the invoice, for the exchange
difference and for the cash basis entries, but there are redundant
entries addressing the tax.
This occur because when reconciling the payment with the invoice the
system create the cash basis moves and reconcile them. During this inner
reconciliation exchange difference move are created (1) just for the tax
line.
Then the outer reconciliation flow continue and compute the exchange
difference moves, considering all cash basis items created before. A new
couple of journal items will be created to account for the difference in
tax, but this is redundant since it was already covered before (1)

opw-2685570

closes odoo/odoo#79764

Signed-off-by: Olivier Colson <oco@odoo.com>