Audio VTS: run tear-down hooks in LIFO instead of FIFO

class Environment : public ::testing::Environment {

   public:

    using TearDownFunc = std::function<void()>;

    void registerTearDown(TearDownFunc&& tearDown) { tearDowns.push_back(std::move(tearDown)); }

    void registerTearDown(TearDownFunc&& tearDown) { tearDowns.push_front(std::move(tearDown)); }

   private:

    void TearDown() override {