Having both eindDatum and resultaat in the same updateZaak message doesn't work to close zaak

[mericakgul]

In case we have both eindDatum and resultaat doesn't close a zaak.

Scenario: We have a zaak which doesn't have a resultaat. We make an updateZaak request which has both eindDatum and resultaat.

Current behaviour: updatezaak does nothing and the closure doesn't happen and we don't get an error either. It behaves like zaak doesn't have a resultaat but we have already one in the request.

Desired behaviour: the zaak should be closed by using the resultaat in the updateZaak request.

Note: In case the zaak has a resultaat and we make an updateZaak request which has resultaat and eindDatum together again, then the closure doesn't happen once again. Therefore, having resultaat and eindDatum together blocks something and doesn't close the zaak.

Note: After fixing, also check the related test cases and update the assertions accordingly.