**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)
```
const ReplicatedMergeTreeLogEntryData & entry, bool wait_for_non_active)
{
    LOG_DEBUG(log, "Waiting for all replicas to process {}", entry.znode_name);
    auto zookeeper = getZooKeeper();
    Strings replicas = zookeeper->getChildren(zookeeper_path + "/replicas");
    Strings unwaited;
    for (const String & replica : replicas)
    {
        if (wait_for_non_active || zookeeper->exists(zookeeper_path + "/replicas/" + replica + "/is_active"))
        {
            if (!waitForReplicaToProcessLogEntry(replica, entry, wait_for_non_active))
                unwaited.push_back(replica);
        }
        else
        {
            unwaited.push_back(replica);
        }
    }
    LOG_DEBUG(log, "Finished waiting for all replicas to process {}", entry.znode_name);
    return unwaited;
}
bool StorageReplicatedMergeTree::waitForReplicaToProcessLogEntry(