[FIX] POS order return impossible (pos_orderline_absolute_discount)

[vincent-mundo]

Hello, here is a pull request to validate an article return with or without "absolute_discount".

At the beginning the return of article was possible only when there was an absolute_discount (discount by number, not percentage).

Now there is the return no matter what. I tested it in all possibilities, from ticket to invoice.

Thanks

[flotho]

thanks @yelizariev , we're going to have a look to this with @gaelTorrecillas

[flotho]

I think we can close this one because it was not totally correct. The #1485 is really better @yelizariev