[Misc] centralize all usage of environment variables (#4548)

vllm/transformers_utils/tokenizer.py

@@ -5,7 +5,7 @@ import huggingface_hub
 from transformers import (AutoTokenizer, PreTrainedTokenizer,
                           PreTrainedTokenizerFast)
 
-from vllm.config import VLLM_USE_MODELSCOPE
+from vllm.envs import VLLM_USE_MODELSCOPE
 from vllm.logger import init_logger
 from vllm.lora.request import LoRARequest
 from vllm.transformers_utils.tokenizers import BaichuanTokenizer