Early on in “ Atonement ,” there’s a battle so mired in the helter-skelter chaos of combat violence that it puts us right in the fog of war. Near the start of the conflict in Iraq in 2003, we’ve spent a few scenes getting to know the Khachaturians, a boisterous Iraqi family that’s jammed three generations of itself into a single home in Baghdad, all to stay out of harm’s way. But then a bomb blast intrudes, and the family members jump into cars and head across town, to where they think it will