**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::CreateMode::Persistent));
        ops.emplace_back(zkutil::makeCreateRequest(replica_path + "/flags", "",
            zkutil::CreateMode::Persistent));
        ops.emplace_back(zkutil::makeCreateRequest(replica_path + "/is_lost", "0",
            zkutil::CreateMode::Persistent));
        ops.emplace_back(zkutil::makeCreateRequest(replica_path + "/metadata", metadata_str,
            zkutil::CreateMode::Persistent));
        ops.emplace_back(zkutil::makeCreateRequest(replica_path + "/columns", metadata_snapshot->getColumns().toString(),
            zkutil::CreateMode::Persistent));
        ops.emplace_back(zkutil::makeCreateRequest(replica_path + "/metadata_version", std::to_string(metadata_version),
            zkutil::CreateMode::Persistent));
        Coordination::Responses responses;
        auto code = zookeeper->tryMulti(ops, responses);
        if (code == Coordination::Error::ZNODEEXISTS)
        {
            LOG_WARNING(log, "It looks like the table {} was created by another server at the same moment, will retry", zookeeper_path);
            continue;
        }
        else if (code != Coordination::Error::ZOK)
        {
            zkutil::KeeperMultiException::check(code, ops, responses);
        }
        return true;
    }
    
    throw Exception("Cannot create table, because it is created concurrently every time "
                    "or because of wrong zookeeper_path "
                    "or because of logical error", ErrorCodes::REPLICA_IS_ALREADY_EXIST);
}
void StorageReplicatedMergeTree::createReplica(const StorageMetadataPtr & metadata_snapshot)