**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)
```
else
            {
                String desired_checksums_str = zookeeper->get(part_path + "/checksums");
                desired_checksums = MinimalisticDataPartChecksums::deserializeFrom(desired_checksums_str);
            }
            if (source_part_checksums == desired_checksums)
            {
                LOG_TRACE(log, "Found local part {} with the same checksums as {}", source_part->name, part_name);
                part_to_clone = source_part;
            }
        }
    }
    std::function<MutableDataPartPtr()> get_part;
    if (part_to_clone)
    {
        get_part = [&, part_to_clone]()
        {
            return cloneAndLoadDataPartOnSameDisk(part_to_clone, "tmp_clone_", part_info, metadata_snapshot);
        };
    }
    else
    {
        ReplicatedMergeTreeAddress address(zookeeper->get(source_replica_path + "/host"));
        auto timeouts = ConnectionTimeouts::getHTTPTimeouts(global_context);
        auto user_password = global_context.getInterserverCredentials();
        String interserver_scheme = global_context.getInterserverScheme();
        get_part = [&, address, timeouts, user_password, interserver_scheme]()
        {
            if (interserver_scheme != address.scheme)
                throw Exception("Interserver schemes are different: '" + interserver_scheme