**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.

{
    return shared->common_executor;
}
ReadSettings Context::getReadSettings() const
{
    ReadSettings res;
    std::string_view read_method_str = settings.local_filesystem_read_method.value;
    if (auto opt_method = magic_enum::enum_cast<LocalFSReadMethod>(read_method_str))
        res.local_fs_method = *opt_method;
    else
        throw Exception(ErrorCodes::UNKNOWN_READ_METHOD, "Unknown read method '{}' for local filesystem", read_method_str);
    read_method_str = settings.remote_filesystem_read_method.value;
    if (auto opt_method = magic_enum::enum_cast<RemoteFSReadMethod>(read_method_str))
        res.remote_fs_method = *opt_method;
    else
        throw Exception(ErrorCodes::UNKNOWN_READ_METHOD, "Unknown read method '{}' for remote filesystem", read_method_str);
    res.local_fs_prefetch = settings.local_filesystem_read_prefetch;
    res.remote_fs_prefetch = settings.remote_filesystem_read_prefetch;
    res.remote_fs_read_max_backoff_ms = settings.remote_fs_read_max_backoff_ms;
    res.remote_fs_read_backoff_max_tries = settings.remote_fs_read_backoff_max_tries;
    res.local_fs_buffer_size = settings.max_read_buffer_size;
    res.direct_io_threshold = settings.min_bytes_to_use_direct_io;
    res.mmap_threshold = settings.min_bytes_to_use_mmap_io;
    res.priority = settings.read_priority;
    res.mmap_cache = getMMappedFileCache().get();
    return res;
}
}