One of our users just killed mutations produced by `ALTER MODIFY` queries on 21 servers. After that new alters on three servers stuck with:
```
Cannot execute alter metadata with version: 8 because another alter 7 must be executed before
```

However, there is no corresponding alter №7 in the replication queue and no undone mutations:
```
select * from system.mutations where is_done = 0
```

However, in the ZooKeeper, we have the correct state of metadata_version:
```
Row 13:
───────
name:           metadata_version
value:          7
czxid:          23078663291
mzxid:          29401964979
ctime:          2020-09-02 17:52:08
mtime:          2020-11-13 00:43:18
version:        7
cversion:       0
aversion:       0
ephemeralOwner: 0
dataLength:     1
numChildren:    0
pzxid:          23078663291
```
`SYSTEM RESTART REPLICA dbname.table_name` solves the issue, but it seems like` KILL MUTATION` in some cases can lead to unfinished alter.
if (current_mutation_it == mutations_by_znode.end())
        return {};
    const MutationStatus & status = current_mutation_it->second;
    MergeTreeMutationStatus result
    {
        .is_done = status.is_done,
        .latest_failed_part = status.latest_failed_part,
        .latest_fail_time = status.latest_fail_time,
        .latest_fail_reason = status.latest_fail_reason,
    };
    if (mutation_ids && !status.latest_fail_reason.empty())
    {
        const auto & latest_failed_part_info = status.latest_failed_part_info;
        auto in_partition = mutations_by_partition.find(latest_failed_part_info.partition_id);
        if (in_partition != mutations_by_partition.end())
        {
            const auto & version_to_status = in_partition->second;
            auto begin_it = version_to_status.upper_bound(latest_failed_part_info.getDataVersion());
            for (auto it = begin_it; it != version_to_status.end(); ++it)
            {
                
                if (!it->second->is_done && it->second->latest_fail_reason == status.latest_fail_reason)
                    mutation_ids->insert(it->second->entry->znode_name);
            }
        }
    }
    return result;
}
std::vector<MergeTreeMutationStatus> ReplicatedMergeTreeQueue::getMutationsStatus() const