cache eviction for destroyed volume fails.

If a volume has been already destroyed and eviction later is called and choose a node from this volume, the eviction will hit the SIGSEGV
`[](const sisl::CacheRecord& rec) -> bool {
                    const auto& hnode = (sisl::SingleEntryHashNode< BtreeNodePtr >&)rec;
                    return static_cast< IndexBtreeNode* >(hnode.m_value.get())->m_idx_buf->is_clean();
                }},`