Auto handle PD disaggregation in bench_serving (#6587)

Co-authored-by: yizhang2077 <1109276519@qq.com>

python/sglang/bench_serving.py

@@ -1304,12 +1304,10 @@ async def benchmark(
     if "sglang" in backend:
         server_info = requests.get(base_url + "/get_server_info")
         if server_info.status_code == 200:
-            if pd_separated:
-                accept_length = server_info.json()["decode"][0]["internal_states"][
-                    0
-                ].get("avg_spec_accept_length", None)
-            else:
-                accept_length = server_info.json()["internal_states"][0].get(
+            server_info_json = server_info.json()
+            if "decode" in server_info_json:
+                server_info_json = server_info_json["decode"][0]
+            accept_length = server_info_json["internal_states"][0].get(
                 "avg_spec_accept_length", None
             )
         else:

scripts/playground/disaggregation/cli-logprob.py

-prompt = "The capital of taiwan is "
+prompt = "The capital of france is "
 
 import json