[minor] sync code on python/sglang/test/test_deterministic.py and improve ci tests (#11777)

Co-authored-by: Stefan He <hebiaobuaa@gmail.com>
Co-authored-by: Byron Hsu <byronhsu1230@gmail.com>

python/sglang/srt/server_args.py

@@ -509,6 +509,11 @@ class ServerArgs:
         """
         Orchestrates the handling of various server arguments, ensuring proper configuration and validation.
         """
+
+        if self.model_path.lower() in ["none", "dummy"]:
+            # Skip for dummy models
+            return
+
         # Handle deprecated arguments.
         self._handle_deprecated_args()