Method lru_remove

src/common/shared_cache.hpp:63–70

  }

  void lru_remove(const K& key) {
    auto i = contents.find(key);
    if (i == contents.end())
      return;
    lru.erase(i->second);
    --size;
    contents.erase(i);
  }

  void lru_add(const K& key, const VPtr& val, std::list<VPtr> *to_release) {
    auto i = contents.find(key);