Add retry for flaky tests in CI (#4755)

test/srt/test_data_parallelism.py

@@ -10,11 +10,12 @@ from sglang.test.test_utils import (
     DEFAULT_MODEL_NAME_FOR_TEST,
     DEFAULT_TIMEOUT_FOR_SERVER_LAUNCH,
     DEFAULT_URL_FOR_TEST,
+    CustomTestCase,
     popen_launch_server,
 )
 
 
-class TestDataParallelism(unittest.TestCase):
+class TestDataParallelism(CustomTestCase):
     @classmethod
     def setUpClass(cls):
         cls.model = DEFAULT_MODEL_NAME_FOR_TEST