Configuration:
- Company Currency: MXN
- Tax 16%.
- Multicurrency, MXN and USD.
- Decimal precision: 4
- Currency Data:
MXN: rate 1.0
USD rates

| Database time | rate | Local time (Mexico) | 
| --- | --- | --- |
| 2016-09-09 00:00:01 | 0.054440 | 2016-09-08 17:00:01 |
| 2016-10-11 00:00:01 | 0.051815 | 2016-10-10 17:00:01 |

Steps to reproduce:

1. Create an invoice for 600 USD  + tax (16%) with date 09/09/16 (September 9, 2016) and when you validate in the journal entry is $12,784.7172 MXN.
3. Create a bank statement in MXN and add a line with date 11/10/16 (October 11, 2016) and amount $13,372.80 MXN.
4. When reconcile select the invoice and there is a difference ($588.0828 MXN) add a line with the difference and select an account for the difference. 
<img width="607" alt="captura de pantalla 2016-11-04 a la s 17 23 26" src="https://cloud.githubusercontent.com/assets/6758279/20025385/749605a2-a2b3-11e6-8b1a-4e9fbf1521ed.png">

**Note that the amount of difference is $588.08 in when you select the account**

5. Click on reconcile.

Expected behavior:
- Reconcile the invoice and create account move.

Current behavior:
- Raise an error  `Wrong credit or debit value in accounting entry !`

![captura de pantalla 2016-11-01 a la s 19 18 52](https://cloud.githubusercontent.com/assets/6758279/19913537/1c272866-a069-11e6-9b06-5851681c7fa5.png)

addons/account/models/account_move.py
'debit': amount_diff < 0 and -amount_diff or 0.0,
                'credit': amount_diff > 0 and amount_diff or 0.0,
                'account_id': rec.debit_move_id.account_id.id,
                'move_id': move.id,
                'currency_id': currency.id,
                'amount_currency': -diff_in_currency,
                'partner_id': rec.debit_move_id.partner_id.id,
            })
            rec.env['account.move.line'].create({
                'name': _('Currency exchange rate difference'),
                'debit': amount_diff > 0 and amount_diff or 0.0,
                'credit': amount_diff < 0 and -amount_diff or 0.0,
                'account_id': amount_diff > 0 and rec.company_id.currency_exchange_journal_id.default_debit_account_id.id or rec.company_id.currency_exchange_journal_id.default_credit_account_id.id,
                'move_id': move.id,
                'currency_id': currency.id,
                'amount_currency': diff_in_currency,
                'partner_id': rec.debit_move_id.partner_id.id,
            })
            for aml in aml_to_fix:
                partial_rec = rec.env['account.partial.reconcile'].create({
                    'debit_move_id': aml.credit and line_to_reconcile.id or aml.id,
                    'credit_move_id': aml.debit and line_to_reconcile.id or aml.id,
                    'amount': abs(aml.amount_residual),
                    'amount_currency': abs(aml.amount_residual_currency),
                    'currency_id': currency.id,
                })
            move.post()
        return line_to_reconcile.id, partial_rec.id
    @api.model
    def create(self, vals):