**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)
```
}
    found_part_name = largest_part_found;
    return largest_replica_found;
}
/** If a quorum is tracked for a part, update information about it in ZK.
  */
void StorageReplicatedMergeTree::updateQuorum(const String & part_name, bool is_parallel)
{
    auto zookeeper = getZooKeeper();
    
    String quorum_status_path = zookeeper_path + "/quorum/status";
    if (is_parallel)
        quorum_status_path = zookeeper_path + "/quorum/parallel/" + part_name;
    
    const String quorum_last_part_path = zookeeper_path + "/quorum/last_part";
    String value;
    Coordination::Stat stat;
    
    while (zookeeper->tryGet(quorum_status_path, value, &stat))
    {
        ReplicatedMergeTreeQuorumEntry quorum_entry(value);
        if (quorum_entry.part_name != part_name)
        {
            
            break;
        }
        quorum_entry.replicas.insert(replica_name);
        if (quorum_entry.replicas.size() >= quorum_entry.required_number_of_replicas)
        {