Currently, killing a child session doesn't interrupt its parent session or other child sessions. This behavior was introduced in SERVER-66777 to prevent the reaping expired child sessions to interrupt active (parent or child) sessions. However, this has led to deadlock in BF-28922 where a session should have been interrupted by stepdown and wasn't because of this logic. Given that reaping expired child sessions is the only case (that we know of) where killing a child session shouldn't interrupt its parent session or other child sessions, we should make killing a child session interrupt all sessions associated with it in all other cases.