async_quest_layers: Subroute calc broken

[Axiangel]

After a single pass of a quest area using coords in master branch, MAD will recalculate the route into a subroute with only stops without known quests and use this subroute for the next pass. In async_quest_layers the procedure is similar, only that the subroute generated will still contain all the coords from the original route, forcing the scanner to revisit all of them even if the quest is known.