Does the extra effect in Scavenging lead to 2 discards?
You will only discard one card as that is all the crossfire rule calls for. If you notice it specifies how many cards to draw based on the game setup and it specifies how many to discard under all game setups. 

For the normal version you discard then draw meaning you won't discard what you will draw. Also you can draw the card you just discarded. 

For the hard version you draw then discard meaning you can discard a card you just drew.