**Describe the bug**
For DATABASE ENGINE Atomic (used by Default for all databases from 20.10) 
when try to `DROP TALBE replicatedmergetree table ON CLUSTER ... SYNC`, query failed after `distributed_ddl_task_timeout` seconds
`decrease `database_atomic_delay_before_drop_table_sec=1` and setup `database_atomic_wait_for_drop_and_detach_synchronously=1` for default user profile didn't help

**How to reproduce**
just look to https://gist.github.com/Slach/a7f2946a108883f6b1d5585b1b5b6b0d
```
bash -x ./reproduce.sh
```

* Which ClickHouse server version to use
Latest official docker build

* Non-default settings, if any
```
<yandex>
    <database_atomic_delay_before_drop_table_sec>1</database_atomic_delay_before_drop_table_sec>
    <profile>
        <default>
            <database_atomic_wait_for_drop_and_detach_synchronously>1</database_atomic_wait_for_drop_and_detach_synchronously>
            <distributed_ddl_task_timeout>20</distributed_ddl_task_timeout>
        </default>
    </profile>
</yandex>

```

**Expected behavior**
Successfull DROP TABLE on cluster

**Error message and/or stacktrace**
Code: 159. DB::Exception: Received from localhost:9000. DB::Exception: Watching task /clickhouse/task_queue/ddl/query-0000000001 is executing longer than distributed_ddl_task_timeout (=20) seconds. There are 2 unfinished hosts (0 of them are currently active), they are going to execute the query in background.

**Additional context**
table physically deleted, but Atomic engine doesn't return "finished" flag to Zookeeper `distributed_ddl` queue

```
docker-compose exec clickhouse-0-0-0 clickhouse-client -q "SELECT * FROM system.zookeeper WHERE path='/clickhouse/task_queue/ddl/query-0000000001/finished' FORMAT
Vertical"
```

returns empty result


{
            LOG_DEBUG(log, "Will not execute task {}: {}", entry_name, reason);
            saveTask(entry_name);
            continue;
        }
        bool already_processed = zookeeper->exists(fs::path(task->entry_path)  / "finished" / task->host_id_str);
        if (!server_startup && !task->was_executed && already_processed)
        {
            throw Exception(ErrorCodes::LOGICAL_ERROR,
                "Server expects that DDL task {} should be processed, but it was already processed according to ZK",
                entry_name);
        }
        if (!already_processed)
        {
            worker_pool->scheduleOrThrowOnError([this, task_ptr = task.release()]()
            {
                setThreadName("DDLWorkerExec");
                enqueueTask(DDLTaskPtr(task_ptr));
            });
        }
        else
        {
            LOG_DEBUG(log, "Task {} ({}) has been already processed", entry_name, task->entry.query);
        }
        saveTask(entry_name);
        if (stop_flag)
            break;
    }
}
void DDLWorker::saveTask(const String & entry_name)