Model config is logged twice on startup
Currently, the model config is logged twice during startup:

1. via `AutoConfig.from_pretrained`
2. via `AutoTokenizer.from_pretrained` -> `AutoConfig.from_pretrained`

Should there be a state variable that prevents the logging of the same config twice?

This happens for example with all example scripts:

Example log when running `run_clm.py`:
```
  File "examples/language-modeling/run_clm.py", line 444, in <module>
    main()
  File "examples/language-modeling/run_clm.py", line 275, in main
    config = AutoConfig.from_pretrained(model_args.model_name_or_path, **config_kwargs)
  File "/mnt/nvme1/code/huggingface/transformers-gpt-neo-nan/src/transformers/models/auto/configuration_auto.py", line 401, in from_pretrained
    return config_class.from_dict(config_dict, **kwargs)
  File "/mnt/nvme1/code/huggingface/transformers-gpt-neo-nan/src/transformers/configuration_utils.py", line 526, in from_dict
    traceback.print_stack()
[INFO|configuration_utils.py:527] 2021-04-06 21:16:04,999 >> Model config GPT2Config {
  "_num_labels": 1,
  "activation_function": "gelu_new",
  "architectures": [
    "GPT2LMHeadModel"
  ],
  "attn_pdrop": 0.1,
  "bos_token_id": 50256,
  "embd_pdrop": 0.1,
  "eos_token_id": 50256,
  "gradient_checkpointing": false,
  "id2label": {
    "0": "LABEL_0"
  },
  "initializer_range": 0.02,
  "label2id": {
    "LABEL_0": 0
  },
  "layer_norm_epsilon": 1e-05,
  "model_type": "gpt2",
  "n_ctx": 1024,
  "n_embd": 768,
  "n_head": 12,
  "n_inner": null,
  "n_layer": 6,
  "n_positions": 1024,
  "resid_pdrop": 0.1,
  "summary_activation": null,
  "summary_first_dropout": 0.1,
  "summary_proj_to_labels": true,
  "summary_type": "cls_index",
  "summary_use_proj": true,
  "task_specific_params": {
    "text-generation": {
      "do_sample": true,
      "max_length": 50
    }
  },
  "transformers_version": "4.5.0",
  "use_cache": true,
  "vocab_size": 50257
}

[INFO|configuration_utils.py:490] 2021-04-06 21:16:05,277 >> loading configuration file https://huggingface.co/distilgpt2/resolve/main/config.json from cache at /home/stas/.cache/huggingface/transformers/f985248d2791fcff97732e4ee263617adec1edb5429a2b8421734c6d14e39bee.422318838d1ec4e061efb4ea29671cb2a044e244dc69229682bebd7cacc81631
  File "examples/language-modeling/run_clm.py", line 444, in <module>
    main()
  File "examples/language-modeling/run_clm.py", line 289, in main
    tokenizer = AutoTokenizer.from_pretrained(model_args.model_name_or_path, **tokenizer_kwargs)
  File "/mnt/nvme1/code/huggingface/transformers-gpt-neo-nan/src/transformers/models/auto/tokenization_auto.py", line 390, in from_pretrained
    config = AutoConfig.from_pretrained(pretrained_model_name_or_path, **kwargs)
  File "/mnt/nvme1/code/huggingface/transformers-gpt-neo-nan/src/transformers/models/auto/configuration_auto.py", line 401, in from_pretrained
    return config_class.from_dict(config_dict, **kwargs)
  File "/mnt/nvme1/code/huggingface/transformers-gpt-neo-nan/src/transformers/configuration_utils.py", line 526, in from_dict
    traceback.print_stack()
[INFO|configuration_utils.py:527] 2021-04-06 21:16:05,279 >> Model config GPT2Config {
  "_num_labels": 1,
  "activation_function": "gelu_new",
  "architectures": [
    "GPT2LMHeadModel"
  ],
  "attn_pdrop": 0.1,
  "bos_token_id": 50256,
  "embd_pdrop": 0.1,
  "eos_token_id": 50256,
  "gradient_checkpointing": false,
  "id2label": {
    "0": "LABEL_0"
  },
  "initializer_range": 0.02,
  "label2id": {
    "LABEL_0": 0
  },
  "layer_norm_epsilon": 1e-05,
  "model_type": "gpt2",
  "n_ctx": 1024,
  "n_embd": 768,
  "n_head": 12,
  "n_inner": null,
  "n_layer": 6,
  "n_positions": 1024,
  "resid_pdrop": 0.1,
  "summary_activation": null,
  "summary_first_dropout": 0.1,
  "summary_proj_to_labels": true,
  "summary_type": "cls_index",
  "summary_use_proj": true,
  "task_specific_params": {
    "text-generation": {
      "do_sample": true,
      "max_length": 50
    }
  },
  "transformers_version": "4.5.0",
  "use_cache": true,
  "vocab_size": 50257
}
```

To get the traceback I just added:
```
        import traceback
        traceback.print_stack()
```

@LysandreJik, @sgugger 
Yes, this is known and on the roadmap for the tokenizers: the goal is for them to use their specific config instead of the model config. Hoping to get to that in the next month or so!