[1.6.7] Flamethrower usage speed

[slowclapman]

I am not quite sure if this is actually a bug but the Flamethrower sustain has "instant" usage speed while both shockstaff and boltgun have "steamtech" usage speed

edit: this causes weird things like being able to "fire" it when being disarmed, which will activate the sustain and attempt to attack but to no effect