**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)
```
}
    }
    zkutil::AsyncResponses<Coordination::RemoveResponse> to_delete_futures;
    for (auto & pair : get_futures)
    {
        const String & path = pair.first;
        auto result = pair.second.get();
        if (result.error == Coordination::Error::ZNONODE)
            continue;
        ReadBufferFromString buf(result.data);
        Int64 block_num = 0;
        bool parsed = tryReadIntText(block_num, buf) && buf.eof();
        if (!parsed || (min_block_num <= block_num && block_num <= max_block_num))
            to_delete_futures.emplace_back(path, zookeeper.asyncTryRemove(path));
    }
    for (auto & pair : to_delete_futures)
    {
        const String & path = pair.first;
        Coordination::Error rc = pair.second.get().error;
        if (rc == Coordination::Error::ZNOTEMPTY)
        {
             
            zookeeper.removeRecursive(path);
        }
        else if (rc != Coordination::Error::ZOK)
            LOG_WARNING(log, "Error while deleting ZooKeeper path `{}`: {}, ignoring.", path, Coordination::errorMessage(rc));
    }
    LOG_TRACE(log, "Deleted {} deduplication block IDs in partition ID {}", to_delete_futures.size(), partition_id);
}
void StorageReplicatedMergeTree::replacePartitionFrom(