**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)
```
new_ops.emplace_back(zkutil::makeRemoveRequest(part_path, -1));
            }
            
            new_ops.insert(new_ops.end(), ops.begin(), ops.end());
            ops = std::move(new_ops);
        }
        try
        {
            zookeeper->multi(ops);
            return transaction.commit();
        }
        catch (const zkutil::KeeperMultiException & e)
        {
            size_t num_check_ops = 2 * absent_part_paths_on_replicas.size();
            size_t failed_op_index = e.failed_op_index;
            if (failed_op_index < num_check_ops && e.code == Coordination::Error::ZNODEEXISTS)
            {
                LOG_INFO(log, "The part {} on a replica suddenly appeared, will recheck checksums", e.getPathForFirstFailedOp());
            }
            else
                throw;
        }
    }
}
String StorageReplicatedMergeTree::getChecksumsForZooKeeper(const MergeTreeDataPartChecksums & checksums) const
{
    return MinimalisticDataPartChecksums::getSerializedString(checksums,
        getSettings()->use_minimalistic_checksums_in_zookeeper);
}
bool StorageReplicatedMergeTree::executeLogEntry(LogEntry & entry)