Toggles "at war" status for a faction.

"At War" status determines whether members of a faction can be attacked. Normal interactions (as with merchants, questgivers, etc.) are not available if the player is "at war" with an NPC's faction.

This function does nothing for faction headers or factions for which changing "at war" status is not currently allowed; i.e., factions for which the eighth (canToggleAtWar) return of GetFactionInfo is false or nil.