**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)
```
adding_parts_active_set.add(part_desc->new_part_name);
            part_name_to_desc.emplace(part_desc->new_part_name, part_desc);
            continue;
        }
        
        String replica = findReplicaHavingPart(part_desc->new_part_name, true);
        String found_part_name;
        
        if (replica.empty())
        {
            LOG_DEBUG(log, "Part {} is not found on remote replicas", part_desc->new_part_name);
            
            replica = findReplicaHavingCoveringPart(part_desc->new_part_name, true, found_part_name);
            if (replica.empty())
            {
                
                LOG_DEBUG(log, "Parts covering {} are not found on remote replicas", part_desc->new_part_name);
                continue;
            }
        }
        else
        {
            found_part_name = part_desc->new_part_name;
        }
        part_desc->found_new_part_name = found_part_name;
        part_desc->found_new_part_info = MergeTreePartInfo::fromPartName(found_part_name, format_version);
        part_desc->replica = replica;
        adding_parts_active_set.add(part_desc->found_new_part_name);
        part_name_to_desc.emplace(part_desc->found_new_part_name, part_desc);
    }