match knockback mechanism to vanilla

[Blackjack200]

vanilla knock back function

vanilla force

 public void knockback(double d0, double d1, double d2) {
      d0 *= 1.0D - this.getAttributeValue(Attributes.KNOCKBACK_RESISTANCE);
      if (!(d0 <= 0.0D)) {
         this.hasImpulse = true;
         Vec3 vec3 = this.getDeltaMovement();
         Vec3 vec31 = (new Vec3(d1, 0.0D, d2)).normalize().scale(d0);
         this.setDeltaMovement(vec3.x / 2.0D - vec31.x, this.onGround() ? Math.min(0.4D, vec3.y / 2.0D + d0) : vec3.y, vec3.z / 2.0D - vec31.z);
      }
   }

this.knockback((double)0.4F, d0, d1);