[FIX] Allow default values for payment mode in multi-company env

[CasVissers-360ERP]

If using ir.default for payment mode in a multi-company environment the payment mode of a sister company could be loaded if superuser (uid 1) was active in this sister company. Resulting in the error message:
_("The company of the invoice %s does not match with that of the payment mode") % rec.name)

This PR fixes this issue.

[pedrobaeza]

Please indicate steps to reproduce the problem. I don't think populating company_id in the refund fields is the solution to your problem.

[CasVissers-360ERP]

@pedrobaeza I would like to create a runbot video, but OCA runbot seems not accessible?

[pedrobaeza]

You can use the "Try me on runbot" button. Any way, I still prefer written steps than a hard to follow video. And as said, a technical explanation why this solves the problem is also welcome (included as comment/docstring of the method as well for future references).