**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)
```
quorum_str = zookeeper->get(quorum_parallel_path, &quorum_stat);
                        quorum_path = quorum_parallel_path;
                    }
                    quorum_entry.fromString(quorum_str);
                    if (quorum_entry.part_name == entry.new_part_name)
                    {
                        ops.emplace_back(zkutil::makeRemoveRequest(quorum_path, quorum_stat.version));
                        auto part_info = MergeTreePartInfo::fromPartName(entry.new_part_name, format_version);
                        if (part_info.min_block != part_info.max_block)
                            throw Exception("Logical error: log entry with quorum for part covering more than one block number",
                                ErrorCodes::LOGICAL_ERROR);
                        ops.emplace_back(zkutil::makeCreateRequest(
                            zookeeper_path + "/quorum/failed_parts/" + entry.new_part_name,
                            "",
                            zkutil::CreateMode::Persistent));
                        
                        if (!entry.block_id.empty() && zookeeper->exists(zookeeper_path + "/blocks/" + entry.block_id))
                            ops.emplace_back(zkutil::makeRemoveRequest(zookeeper_path + "/blocks/" + entry.block_id, -1));
                        Coordination::Responses responses;
                        auto code = zookeeper->tryMulti(ops, responses);
                        if (code == Coordination::Error::ZOK)
                        {
                            LOG_DEBUG(log, "Marked quorum for part {} as failed.", entry.new_part_name);
                            queue.removeFromVirtualParts(part_info);
                            return true;
                        }
                        else if (code == Coordination::Error::ZBADVERSION || code == Coordination::Error::ZNONODE || code == Coordination::Error::ZNODEEXISTS)
                        {
                            LOG_DEBUG(log, "State was changed or isn't expected when trying to mark quorum for part {} as failed. Code: {}", entry.new_part_name, Coordination::errorMessage(code));
                        }