**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)
```
mutation_entry.create_time = time(nullptr);
            ops.emplace_back(zkutil::makeSetRequest(mutations_path, String(), mutations_stat.version));
            ops.emplace_back(
                zkutil::makeCreateRequest(mutations_path + "/", mutation_entry.toString(), zkutil::CreateMode::PersistentSequential));
        }
        Coordination::Responses results;
        Coordination::Error rc = zookeeper->tryMulti(ops, results);
        if (rc == Coordination::Error::ZOK)
        {
            if (alter_entry->have_mutation)
            {
                
                String alter_path = dynamic_cast<const Coordination::CreateResponse &>(*results[2]).path_created;
                alter_entry->znode_name = alter_path.substr(alter_path.find_last_of('/') + 1);
                
                String mutation_path = dynamic_cast<const Coordination::CreateResponse &>(*results.back()).path_created;
                mutation_znode = mutation_path.substr(mutation_path.find_last_of('/') + 1);
            }
            else
            {
                
                String alter_path = dynamic_cast<const Coordination::CreateResponse &>(*results.back()).path_created;
                alter_entry->znode_name = alter_path.substr(alter_path.find_last_of('/') + 1);
            }
            break;
        }
        else if (rc == Coordination::Error::ZBADVERSION)
        {
            if (results[0]->error != Coordination::Error::ZOK)
                throw Exception("Metadata on replica is not up to date with common metadata in Zookeeper. Cannot alter",