**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)
```
const ASTPtr & partition,
    const StorageMetadataPtr & metadata_snapshot,
    const String & from_,
    const Context & query_context)
{
    String from = from_;
    if (from.empty())
        throw Exception("ZooKeeper path should not be empty", ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);
    String partition_id = getPartitionIDFromQuery(partition, query_context);
    zkutil::ZooKeeperPtr zookeeper;
    if (from[0] != '/')
    {
        auto delimiter = from.find(':');
        if (delimiter == String::npos)
            throw Exception("Zookeeper path should start with '/' or '<auxiliary_zookeeper_name>:/'", ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);
        auto auxiliary_zookeeper_name = from.substr(0, delimiter);
        from = from.substr(delimiter + 1, String::npos);
        if (from.empty())
            throw Exception("ZooKeeper path should not be empty", ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);
        zookeeper = global_context.getAuxiliaryZooKeeper(auxiliary_zookeeper_name);
        LOG_INFO(log, "Will fetch partition {} from shard {} (auxiliary zookeeper '{}')", partition_id, from_, auxiliary_zookeeper_name);
    }
    else
    {
        zookeeper = getZooKeeper();
        LOG_INFO(log, "Will fetch partition {} from shard {}", partition_id, from_);
    }
    if (from.back() == '/')
        from.resize(from.size() - 1);