Failing infrequently on CI but pretty reproducable with
bazel test //test/integration:ads_integration_test --config=clang-tsan --runs_per_test=200 --test_arg=--gtest_filter="IpVersionsClientType/AdsIntegrationTest.DuplicateWarmingListeners/1"

Example failure:
https://circleci.com/gh/envoyproxy/envoy/223256?utm_campaign=workflow-failed&utm_medium=email&utm_source=notification

Actual tsan warning: https://pastebin.com/zWtG77K2

@fredlas I think this might be related to 6879 - could you take a look?