In your Demonbuddy folder go to Plugins/Trinity/Combat/Abilities folder and open the WitchDoctorCombat file in some text editing program. Search for this block of code:
// Zombie Dogs non-sacrifice build
if (!hasSacrifice && CanCast(SNOPower.Witchdoctor_SummonZombieDog) && Trinity.PlayerOwnedZombieDogCount == 0)
Yours will have a number other than 0 for the last part ('Trinity.PlayerOwnedZombieDogCount < 3', I think is the default), change it to be like what I have above. That will make it only summon zombie dog when you have 0 zombie dogs out.