Merge "Fix flaky test RepeatedSetup_KeepChangingPrivateDnsServers" am: fe5b82ec am: 94afd9e3

    enum TlsServerState { WORKING, UNSUPPORTED, UNRESPONSIVE };

    const std::string addr1 = getUniqueIPv4Address();

    const std::string addr2 = getUniqueIPv4Address();

    const auto waitForPrivateDnsStateUpdated = []() {

        // A buffer time for PrivateDnsConfiguration to update its state. It prevents this test

        // being flaky. See b/152009023 for the reason.

        std::this_thread::sleep_for(20ms);

    };

    test::DNSResponder dns1(addr1);

    test::DNSResponder dns2(addr2);

            tls.setHangOnHandshakeForTesting(serverState == UNRESPONSIVE);

            const int connectCountsBefore = tls.acceptConnectionsCount();

            waitForPrivateDnsStateUpdated();

            ResolverParamsParcel parcel = DnsResponderClient::GetDefaultResolverParamsParcel();

            parcel.servers = {config.tlsServer};

            parcel.tlsServers = {config.tlsServer};