Disable two flaky gevent tests

src/python/grpcio_tests/commands.py

@@ -135,7 +135,8 @@ class TestGevent(setuptools.Command):
         # This test will stuck while running higher version of gevent
         'unit._auth_context_test.AuthContextTest.testSessionResumption',
         # TODO(https://github.com/grpc/grpc/issues/15411) enable these tests
-        'unit._metadata_flags_test',
+        'unit._channel_ready_future_test.ChannelReadyFutureTest.test_immediately_connectable_channel_connectivity',
+        "unit._cython._channel_test.ChannelTest.test_single_channel_lonely_connectivity",
         'unit._exit_test.ExitTest.test_in_flight_unary_unary_call',
         'unit._exit_test.ExitTest.test_in_flight_unary_stream_call',
         'unit._exit_test.ExitTest.test_in_flight_stream_unary_call',
@@ -143,6 +144,7 @@ class TestGevent(setuptools.Command):
         'unit._exit_test.ExitTest.test_in_flight_partial_unary_stream_call',
         'unit._exit_test.ExitTest.test_in_flight_partial_stream_unary_call',
         'unit._exit_test.ExitTest.test_in_flight_partial_stream_stream_call',
+        'unit._metadata_flags_test',
         'health_check._health_servicer_test.HealthServicerTest.test_cancelled_watch_removed_from_watch_list',
         # TODO(https://github.com/grpc/grpc/issues/17330) enable these three tests
         'channelz._channelz_servicer_test.ChannelzServicerTest.test_many_subchannels',