Merge "TransactionCompletedListener: Mutex for getInstance" into tm-dev

}

sp<TransactionCompletedListener> TransactionCompletedListener::sInstance = nullptr;

static std::mutex sListenerInstanceMutex;

void TransactionCompletedListener::setInstance(const sp<TransactionCompletedListener>& listener) {

    sInstance = listener;

}

sp<TransactionCompletedListener> TransactionCompletedListener::getInstance() {

    std::lock_guard<std::mutex> lock(sListenerInstanceMutex);

    if (sInstance == nullptr) {

        sInstance = new TransactionCompletedListener;

    }