preserve-rooms: handle room assignment better when both spouses have individual rooms assigned

[myk002]

Reported on Steam: https://steamcommunity.com/app/2346660/discussions/0/6589424052365998664/#c596263145435086791

Right now when a unit leaves the map, we assign that unit's rooms to their spouse if that spouse is on the map. We might not want to do this if the unit and the spouse have separately assigned rooms of the same type.