Simplify tests & Fix trtllm custom allreduce registration (#4252)

python/sglang/srt/_custom_ops.py

@@ -6,10 +6,12 @@ from typing import List, Tuple
 import torch
 import torch.library
 
-from sglang.srt.utils import is_hip, is_hpu
+from sglang.srt.utils import get_bool_env_var, is_hip, is_hpu
 
 logger = logging.getLogger(__name__)
-use_vllm_custom_allreduce = os.environ.get("USE_VLLM_CUSTOM_ALLREDUCE", default=True)
+use_vllm_custom_allreduce = get_bool_env_var(
+    "USE_VLLM_CUSTOM_ALLREDUCE", default="true"
+)
 
 if not is_hpu():
     # ROCm does not use vllm custom allreduce