**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)
```
ops.clear();
            responses.clear();
            ops.emplace_back(zkutil::makeRemoveRequest(zookeeper_path + "/dropped", -1));
            ops.emplace_back(zkutil::makeRemoveRequest(zookeeper_path, -1));
            code = zookeeper->tryMulti(ops, responses);
            if (code == Coordination::Error::ZNONODE)
            {
                LOG_WARNING(logger, "Table {} is already finished removing by another replica right now", remote_replica_path);
            }
            else if (code == Coordination::Error::ZNOTEMPTY)
            {
                LOG_ERROR(logger, "Table was not completely removed from ZooKeeper, {} still exists and may contain some garbage.",
                          zookeeper_path);
            }
            else if (code != Coordination::Error::ZOK)
            {
                
                zkutil::KeeperMultiException::check(code, ops, responses);
            }
            else
            {
                LOG_INFO(logger, "Table {} was successfully removed from ZooKeeper", zookeeper_path);
            }
        }
    }
}
/** Verify that list of columns and table storage_settings_ptr match those specified in ZK (/metadata).
  * If not, throw an exception.
  */
void StorageReplicatedMergeTree::checkTableStructure(const String & zookeeper_prefix, const StorageMetadataPtr & metadata_snapshot)