**Describe the bug**
The ClickHouse client freezes when executing `ALTER TABLE` with `ADD COLUMN` and `MODIFY ORDER` on a table built using Replicated Versioned Collapsing Merge Tree engine.

**How to reproduce**
* ClickHouse client version 20.10.1.1.
Connecting to localhost:9000 as user default.
Connected to ClickHouse server version 20.10.1 revision 54440.

* `CREATE TABLE` statements
```
SHOW CREATE TABLE table0

┌─statement──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
│ CREATE TABLE default.table0
(
    `d` Date,
    `a` String,
    `b` UInt8,
    `x` String,
    `y` Int8,
    `version` UInt64,
    `sign` Int8 DEFAULT 1
)
ENGINE = ReplicatedVersionedCollapsingMergeTree('/clickhouse/tables/{shard}/table0', '{replica}', sign, version)
PARTITION BY y
ORDER BY d
SETTINGS index_granularity = 8192 │
└────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘

1 rows in set. Elapsed: 0.004 sec.
```

* Queries to run that lead to unexpected result
```
ALTER TABLE table0 ADD COLUMN order UInt32, MODIFY ORDER BY (d, order)
```
String hash_hex = src_part->checksums.getTotalChecksumHex();
        if (replace)
            LOG_INFO(log, "Trying to replace {} with hash_hex {}", src_part->name, hash_hex);
        else
            LOG_INFO(log, "Trying to attach {} with hash_hex {}", src_part->name, hash_hex);
        String block_id_path = replace ? "" : (zookeeper_path + "/blocks/" + partition_id + "_replace_from_" + hash_hex);
        auto lock = allocateBlockNumber(partition_id, zookeeper, block_id_path);
        if (!lock)
        {
            LOG_INFO(log, "Part {} (hash {}) has been already attached", src_part->name, hash_hex);
            continue;
        }
        UInt64 index = lock->getNumber();
        MergeTreePartInfo dst_part_info(partition_id, index, index, src_part->info.level);
        auto dst_part = cloneAndLoadDataPartOnSameDisk(src_part, TMP_PREFIX, dst_part_info, metadata_snapshot);
        src_parts.emplace_back(src_part);
        dst_parts.emplace_back(dst_part);
        ephemeral_locks.emplace_back(std::move(*lock));
        block_id_paths.emplace_back(block_id_path);
        part_checksums.emplace_back(hash_hex);
    }
    ReplicatedMergeTreeLogEntryData entry;
    {
        auto src_table_id = src_data.getStorageID();
        entry.type = ReplicatedMergeTreeLogEntryData::REPLACE_RANGE;
        entry.source_replica = replica_name;
        entry.create_time = time(nullptr);
        entry.replace_range_entry = std::make_shared<ReplicatedMergeTreeLogEntryData::ReplaceRangeEntry>();
        auto & entry_replace = *entry.replace_range_entry;
        entry_replace.drop_range_part_name = drop_range_fake_part_name;