**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.

{
    if (!zookeeper_path.empty() && zookeeper_path.back() == '/')
        zookeeper_path.resize(zookeeper_path.size() - 1);
    
    if (!zookeeper_path.empty() && zookeeper_path.front() != '/')
        zookeeper_path = "/" + zookeeper_path;
    return zookeeper_path;
}
static String extractZooKeeperName(const String & path)
{
    if (path.empty())
        throw Exception("ZooKeeper path should not be empty", ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);
    auto pos = path.find(':');
    if (pos != String::npos)
    {
        auto zookeeper_name = path.substr(0, pos);
        if (zookeeper_name.empty())
            throw Exception("Zookeeper path should start with '/' or '<auxiliary_zookeeper_name>:/'", ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);
        return zookeeper_name;
    }
    static constexpr auto default_zookeeper_name = "default";
    return default_zookeeper_name;
}
static String extractZooKeeperPath(const String & path)