**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)
```
{
    if (zookeeper->expired())
        throw Exception("Table was not dropped because ZooKeeper session has expired.", ErrorCodes::TABLE_WAS_NOT_DROPPED);
    auto remote_replica_path = zookeeper_path + "/replicas/" + replica;
    LOG_INFO(logger, "Removing replica {}, marking it as lost", remote_replica_path);
    
    
    zookeeper->trySet(zookeeper_path + "/replicas/" + replica + "/is_lost", "1");
    
    zookeeper->tryRemoveRecursive(remote_replica_path);
    if (zookeeper->exists(remote_replica_path))
        LOG_ERROR(logger, "Replica was not completely removed from ZooKeeper, {} still exists and may contain some garbage.", remote_replica_path);
    
    Strings replicas;
    if (Coordination::Error::ZOK != zookeeper->tryGetChildren(zookeeper_path + "/replicas", replicas) || !replicas.empty())
        return;
    LOG_INFO(logger, "{} is the last replica, will remove table", remote_replica_path);
    /** At this moment, another replica can be created and we cannot remove the table.
      * Try to remove /replicas node first. If we successfully removed it,
      * it guarantees that we are the only replica that proceed to remove the table
      * and no new replicas can be created after that moment (it requires the existence of /replicas node).
      * and table cannot be recreated with new /replicas node on another servers while we are removing data,
      * because table creation is executed in single transaction that will conflict with remaining nodes.
      */
    Coordination::Requests ops;