Currency Difference account move in every case?

[Thorsten Vocks (OpenBig.org)]

Use case:

- Invoice with a curency exchange rate of 1.2500
- Payment also with a currency exchange rate of 1.2500
- Cash discount condition (but this shouldn't matter for this problem).

We have autoamted account move for currency difference (see attached screenshot:
line 2 and line 3) also if we definitely do not have a difference of currency exchange rate
between invoice and payment date.

We should not post a currency difference move if there is no difference of exchange rates
between invoice and payment.

Please see screenshot (focus on line 2 and 3).
The line with the cash discount shouldn't matter for this problem.