[FIX] account: do not auto reconcile void writeoff lines

1. Create a vendor bill with 1 line @ 1000$ and Tax 15%. Post.
2. Go to Accounting>vendor>payment. Create a payment to the same
vendor for 1149.99
There is a difference of 0.01 between the payment and the vendor bill.
3. Reconcile bill and payment, but write-off 0.01 and place a tax of 15%
included

The user receive the following error once he click on reconcile.
"Something went wrong! You are trying to reconcile some entries
that are already reconciled."
Indeed the writeoff line create a 0.0 credit/debit tax line which is
automatically reconciled on creation

opw-2267900

closes odoo/odoo#53115

Signed-off-by: Simon Goffin (sig) <sig@openerp.com>