Stop absorbing scent from closed doors.  This creates a loop that will

increase smell infinitely on the opposite side of a door.  Ironically, a
player in the room resets their square to their own smell and prevents the
infinite loop.  But anyway.  This is bad.  We will now correctly ignore
closed doors and therefore calculate squares_used accurately.  Note: Smell
still lingers forever, it just doesn't increase.

Fixes one of the issues being discussed in pull/4704