**Describe the issue**
ClickHouse is unable to start up after upgrading from 20.8 to 21.8. 

There is a replicated table with `:` in zk path and it couldn't be loaded with:

`2021.09.15 03:49:58.435071 [ 633075 ] {} <Error> Application: DB::Exception: Unknown auxiliary ZooKeeper name '/test_prefix'. If it's required it can be added to the section <auxiliary_zookeepers> in config.xml: Cannot attach table `db1`.`table1` from metadata file /var/lib/clickhouse/metadata/db1/table1.sql from query ATTACH TABLE db1.table1 (`field1` String, `date` Date) ENGINE = ReplicatedMergeTree('/test_prefix:db1/{shard}/table1', '{replica}') PARTITION BY toMonth(date) PRIMARY KEY field1 ORDER BY field1 SETTINGS index_granularity = 8192: while loading database `db1` from path /var/lib/clickhouse/metadata/db1
`

**Expected behavior**
ClickHouse server is able to startup after upgrade without schema change. "test_prefix" in "/test_prefix:db1/{shard}/table1" is not interpreted as an auxiliary ZooKeeper name.

|| (log_pointer == max_log_pointer && queue_size < min_queue_size))
            {
                max_log_pointer = log_pointer;
                min_queue_size = queue_size;
                best_replica = replica;
            }
        }
    }
    if (best_replica.empty())
        throw Exception("Logical error: cannot choose best replica.", ErrorCodes::LOGICAL_ERROR);
    LOG_INFO(log, "Found {} replicas, {} of them are active. Selected {} to fetch from.", replicas.size(), active_replicas.size(), best_replica);
    String best_replica_path = fs::path(from) / "replicas" / best_replica;
    
    /** Trying to download these parts.
      * Some of them could be deleted due to the merge.
      * In this case, update the information about the available parts and try again.
      */
    unsigned try_no = 0;
    Strings missing_parts;
    do
    {
        if (try_no)
            LOG_INFO(log, "Some of parts ({}) are missing. Will try to fetch covering parts.", missing_parts.size());
        if (try_no >= query_context->getSettings().max_fetch_partition_retries_count)
            throw Exception("Too many retries to fetch parts from " + best_replica_path, ErrorCodes::TOO_MANY_RETRIES_TO_FETCH_PARTS);
        Strings parts = zookeeper->getChildren(fs::path(best_replica_path) / "parts");
        ActiveDataPartSet active_parts_set(format_version, parts);
        Strings parts_to_fetch;
        if (missing_parts.empty())
        {