Using `--sampling-steps` in 'gen_single_image_diffusion.py` breaks the inference

[beniz]

The scheduler is lacking from the model (or should be gotten from elsewhere):

python3 gen_single_image_diffusion.py --model-in-file /path/to/model/latest_net_G_A.pth --img-width 128 --img-height 128 --gpuid 3 --img-in /path/to/img.jpg --dir-out /data1/beniz/data/test_ddim/

returns

Traceback (most recent call last):
  File "gen_single_image_diffusion.py", line 794, in <module>
    generate(**vars(args))
  File "gen_single_image_diffusion.py", line 189, in generate
    model, opt = load_model(
  File "gen_single_image_diffusion.py", line 96, in load_model
    model.denoise_fn.beta_schedule["test"]["n_timestep"] = sampling_steps
  File "/home/beniz/.local/lib/python3.8/site-packages/torch/nn/modules/module.py", line 1614, in __getattr__
    raise AttributeError("'{}' object has no attribute '{}'".format(
AttributeError: 'PaletteDenoiseFn' object has no attribute 'beta_schedule'

[beniz]

Fixed with ca910d8