Allow rerun of unstable statschannel tests under TSAN

The test_traffic_json and test_traffic_xml occasionally fail when
running under TSAN. This happens in CI and is most likely a result of
some instability that doesn't seem to be easily reproduced.

(cherry picked from commit ec2fc7680a)

bin/tests/system/isctest/mark.py

@@ -47,6 +47,10 @@ def is_dnsrps_available():
     return True
 
 
+def with_tsan(*args):  # pylint: disable=unused-argument
+    return feature_test("--tsan")
+
+
 have_libxml2 = pytest.mark.skipif(
     not feature_test("--have-libxml2"), reason="libxml2 support disabled in the build"
 )

bin/tests/system/statschannel/tests_json.py

@@ -100,5 +100,6 @@ def test_zone_with_many_keys_json(statsport):
     )
 
 
+@isctest.mark.flaky(max_runs=2, rerun_filter=isctest.mark.with_tsan)
 def test_traffic_json(statsport):
     generic.test_traffic(fetch_traffic_json, statsip="10.53.0.2", statsport=statsport)

bin/tests/system/statschannel/tests_xml.py

@@ -130,5 +130,6 @@ def test_zone_with_many_keys_xml(statsport):
     )
 
 
+@isctest.mark.flaky(max_runs=2, rerun_filter=isctest.mark.with_tsan)
 def test_traffic_xml(statsport):
     generic.test_traffic(fetch_traffic_xml, statsip="10.53.0.2", statsport=statsport)