Method iterator

src/includes/dinit-util.h:840–840

    public:
        iterator() noexcept : buckets(nullptr), list_it(), bucket_num(-1) { }
        iterator(bucket_vec *buckets_p, list_iterator_t lit, size_t bucket_p) noexcept
            : buckets(buckets_p), list_it(lit), bucket_num(bucket_p) { }
        iterator(const iterator &) noexcept = default;