**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)
```
message << ": " << disable_reason;
                    LOG_INFO(log, message.str());
                    return handle_noop(message.str());
                }
                ReplicatedMergeTreeLogEntryData merge_entry;
                CreateMergeEntryResult create_result = createLogEntryToMergeParts(
                    zookeeper, future_merged_part.parts,
                    future_merged_part.name, future_merged_part.type, deduplicate,
                    &merge_entry, can_merge.getVersion(), future_merged_part.merge_type);
                if (create_result == CreateMergeEntryResult::MissingPart)
                    return handle_noop("Can't create merge queue node in ZooKeeper, because some parts are missing");
                if (create_result == CreateMergeEntryResult::LogUpdated)
                    continue;
                merge_entries.push_back(std::move(merge_entry));
                break;
            }
            if (try_no == max_retries)
                return handle_noop("Can't create merge queue node in ZooKeeper, because log was updated in every of "
                    + toString(max_retries) + " tries");
        }
    }
    if (query_context.getSettingsRef().replication_alter_partitions_sync != 0)
    {
        
        for (auto & merge_entry : merge_entries)
            waitForAllReplicasToProcessLogEntry(merge_entry, false);
    }
    return true;
}
bool StorageReplicatedMergeTree::executeMetadataAlter(const StorageReplicatedMergeTree::LogEntry & entry)