Remove unsafe cast in Client::createWithSurfaceParent am: a03e1302

                                         sp<IGraphicBufferProducer>* gbp) {

    if (mFlinger->authenticateSurfaceTexture(parent) == false) {

        ALOGE("failed to authenticate surface texture");

        // The extra parent layer check below before returning is to help with debugging

        // b/134888387. Once the bug is fixed the check can be deleted.

        if ((static_cast<MonitoredProducer*>(parent.get()))->getLayer() == nullptr) {

            ALOGE("failed to find parent layer");

        }

        return BAD_VALUE;

    }