Sharpness and Attribute "attackDamage" don't stack

/give @p iron_sword 1 0 {ench:[{id:16,lvl:1}],AttributeModifiers:[{Operation:0,UUIDLeast:1,UUIDMost:1,Amount:6.0,AttributeName:generic.attackDamage,Name:attackDamage}]}

Attribute attackDamage over writes all information of enchantments dealing with attack power. (IE: Sharpness, Smite, Bane of A.)

Keep in mind when dealing with this solution it may be possible to cause another bug where the swords previous damage may stack with both of these.