**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)
```
try
        {
            current_zookeeper = global_context.getZooKeeper();
        }
        catch (...)
        {
            if (!attach)
                dropIfEmpty();
            throw;
        }
    }
    bool skip_sanity_checks = false;
    if (current_zookeeper && current_zookeeper->exists(replica_path + "/flags/force_restore_data"))
    {
        skip_sanity_checks = true;
        current_zookeeper->remove(replica_path + "/flags/force_restore_data");
        LOG_WARNING(log, "Skipping the limits on severity of changes to data parts and columns (flag {}/flags/force_restore_data).", replica_path);
    }
    else if (has_force_restore_data_flag)
    {
        skip_sanity_checks = true;
        LOG_WARNING(log, "Skipping the limits on severity of changes to data parts and columns (flag force_restore_data).");
    }
    loadDataParts(skip_sanity_checks);
    if (!current_zookeeper)
    {
        if (!attach)
        {
            dropIfEmpty();
            throw Exception("Can't create replicated table without ZooKeeper", ErrorCodes::NO_ZOOKEEPER);