avcodec/h264: do not trust last_pic_droppable when marking pictures as done

This simplifies the code and fixes a deadlock

Fixes Ticket2927
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
static void copy_parameter_set(void **to, void **from, int count, int size)
{
    int i;

    for (i = 0; i < count; i++) {
        if (to[i] && !from[i])
            av_freep(&to[i]);
        else if (from[i] && !to[i])
            to[i] = av_malloc(size);

        if (from[i])
            memcpy(to[i], from[i], size);
    }
}

static void copy_parameter_set(void **to, void **from, int count, int size)
{
    int i;

    for (i = 0; i < count; i++) {
        if (to[i] && !from[i])
            av_freep(&to[i]);
        else if (from[i] && !to[i])
            to[i] = av_malloc(size);

        if (from[i])
            memcpy(to[i], from[i], size);
    }
}
