WIP: try not messing with event_loop in tests

Author: vchudnov-g

tests/system/conftest.py

@@ -75,9 +75,9 @@ def async_anonymous_credentials():
     # to it. So, the event loop might close before tests finishes. In the
     # customized version, we don't close the event loop.
 
-    @pytest.fixture
-    def event_loop():
-        return asyncio.get_event_loop()
+    # @pytest.fixture
+    # def event_loop():
+    #     return asyncio.get_event_loop()
 
     @pytest.fixture(params=["grpc_asyncio", "rest_asyncio"])
     def async_echo(use_mtls, request, event_loop):