fix: mark an extruder as used whenever we switch to it (or we start out with it) (CURA-3737)
fix: mark an extruder as used whenever we switch to it (or we start out with it) (CURA-3737)

alephobjects/CuraEngine,Ultimaker/CuraEngine,ROBO3D/CuraEngine,ROBO3D/CuraEngine,Ultimaker/CuraEngine,alephobjects/CuraEngine,alephobjects/CuraEngine,ROBO3D/CuraEngine