[0.0.250] Construction workers don't finish their builds

[nja]

When I give a construction worker an order to prioritize a tile, I expect them to finish the damn tile!  Instead, sometimes (like when they're hungry, or they want to sleep, or they just feel like watering some plants instead) they'll work for about one second, then leave.  Prioritizing a tile should force the worker to finish the construction before moving on.