transfer open offer's challenge when upgraded

Author: woodser

core/src/main/java/haveno/core/offer/OpenOfferManager.java

@@ -2057,6 +2057,7 @@ private void maybeUpdatePersistedOffers() {
                 updatedOffer.setPriceFeedService(priceFeedService);
 
                 OpenOffer updatedOpenOffer = new OpenOffer(updatedOffer, originalOpenOffer.getTriggerPrice());
+                updatedOpenOffer.setChallenge(originalOpenOffer.getChallenge());
                 addOpenOffer(updatedOpenOffer);
                 requestPersistence();