**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)
```
return false;
        --right;
    }
    
    part_info = MergeTreePartInfo(partition_id, left, right, max_level, mutation_version);
    return true;
}
void StorageReplicatedMergeTree::dropPartition(const ASTPtr &, const ASTPtr & partition, bool detach, const Context & query_context)
{
    assertNotReadonly();
    if (!is_leader)
        throw Exception("DROP PARTITION cannot be done on this replica because it is not a leader", ErrorCodes::NOT_A_LEADER);
    zkutil::ZooKeeperPtr zookeeper = getZooKeeper();
    String partition_id = getPartitionIDFromQuery(partition, query_context);
    LogEntry entry;
    if (dropPartsInPartition(*zookeeper, partition_id, entry, detach))
    {
        
        if (query_context.getSettingsRef().replication_alter_partitions_sync != 0)
        {
            if (query_context.getSettingsRef().replication_alter_partitions_sync == 1)
                waitForReplicaToProcessLogEntry(replica_name, entry);
            else
                waitForAllReplicasToProcessLogEntry(entry);
        }
    }
    
    cleanLastPartNode(partition_id);
}
void StorageReplicatedMergeTree::truncate(