**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.

zkutil::Strings replicas;
    zkutil::Strings active_replicas;
    String best_replica;
    {
        
        replicas = zookeeper->getChildren(fs::path(from) / "replicas");
        
        active_replicas.reserve(replicas.size());
        for (const String & replica : replicas)
            if (zookeeper->exists(fs::path(from) / "replicas" / replica / "is_active"))
                active_replicas.push_back(replica);
        if (active_replicas.empty())
            throw Exception("No active replicas for shard " + from, ErrorCodes::NO_ACTIVE_REPLICAS);
        /** You must select the best (most relevant) replica.
        * This is a replica with the maximum `log_pointer`, then with the minimum `queue` size.
        * NOTE This is not exactly the best criteria. It does not make sense to download old partitions,
        *  and it would be nice to be able to choose the replica closest by network.
        * NOTE Of course, there are data races here. You can solve it by retrying.
        */
        Int64 max_log_pointer = -1;
        UInt64 min_queue_size = std::numeric_limits<UInt64>::max();
        for (const String & replica : active_replicas)
        {
            String current_replica_path = fs::path(from) / "replicas" / replica;
            String log_pointer_str = zookeeper->get(fs::path(current_replica_path) / "log_pointer");
            Int64 log_pointer = log_pointer_str.empty() ? 0 : parse<UInt64>(log_pointer_str);
            Coordination::Stat stat;
            zookeeper->get(fs::path(current_replica_path) / "queue", &stat);
            size_t queue_size = stat.numChildren;
            if (log_pointer > max_log_pointer