**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)
```
other_replicas_fixed_granularity = checkFixedGranualrityInZookeeper();
                checkTableStructure(zookeeper_path, metadata_snapshot);
                Coordination::Stat metadata_stat;
                current_zookeeper->get(zookeeper_path + "/metadata", &metadata_stat);
                metadata_version = metadata_stat.version;
            }
            catch (Coordination::Exception & e)
            {
                if (!is_first_replica && e.code == Coordination::Error::ZNONODE)
                    throw Exception("Table " + zookeeper_path + " was suddenly removed.", ErrorCodes::ALL_REPLICAS_LOST);
                else
                    throw;
            }
            if (!is_first_replica)
                createReplica(metadata_snapshot);
        }
        catch (...)
        {
            
            dropIfEmpty();
            throw;
        }
    }
    else
    {
        
        String replica_metadata;
        bool replica_metadata_exists = current_zookeeper->tryGet(replica_path + "/metadata", replica_metadata);
        if (!replica_metadata_exists || replica_metadata.empty())
        {