[CI] Move disaggregation basic CI back to 2-gpu suite (#23447)

python/sglang/test/server_fixtures/disaggregation_fixture.py

@@ -23,6 +23,7 @@ logger = logging.getLogger(__name__)
 class PDDisaggregationServerBase(CustomTestCase):
     @classmethod
     def setUpClass(cls):
+        os.environ["MC_TCP_ENABLE_CONNECTION_POOL"] = "true"
         parsed_url = urlparse(DEFAULT_URL_FOR_TEST)
         cls.base_host = parsed_url.hostname
         base_port = str(parsed_url.port)
@@ -140,6 +141,7 @@ class PDDisaggregationServerBase(CustomTestCase):
 
     @classmethod
     def tearDownClass(cls):
+        os.environ.pop("MC_TCP_ENABLE_CONNECTION_POOL")
         for process in [cls.process_lb, cls.process_decode, cls.process_prefill]:
             if process:
                 try: