[PD] Fix generate endpoint of min_lb for PD (#5598)

Signed-off-by: Shangming Cai <caishangming@linux.alibaba.com>

python/sglang/srt/disaggregation/mini_lb.py

@@ -187,11 +187,11 @@ async def handle_generate_request(request_data: dict):
 
     if request_data.get("stream", False):
         return await load_balancer.generate_stream(
-            modified_request, prefill_server, decode_server
+            modified_request, prefill_server, decode_server, "generate"
         )
     else:
         return await load_balancer.generate(
-            modified_request, prefill_server, decode_server
+            modified_request, prefill_server, decode_server, "generate"
         )