**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 getConfigRef().has("distributed_ddl");
}
void Context::setDDLWorker(std::unique_ptr<DDLWorker> ddl_worker)
{
    auto lock = getLock();
    if (shared->ddl_worker)
        throw Exception("DDL background thread has already been initialized", ErrorCodes::LOGICAL_ERROR);
    ddl_worker->startup();
    shared->ddl_worker = std::move(ddl_worker);
}
DDLWorker & Context::getDDLWorker() const
{
    auto lock = getLock();
    if (!shared->ddl_worker)
    {
        if (!hasZooKeeper())
            throw Exception("There is no Zookeeper configuration in server config", ErrorCodes::NO_ELEMENTS_IN_CONFIG);
        if (!hasDistributedDDL())
            throw Exception("There is no DistributedDDL configuration in server config", ErrorCodes::NO_ELEMENTS_IN_CONFIG);
        throw Exception("DDL background thread is not initialized", ErrorCodes::NO_ELEMENTS_IN_CONFIG);
    }
    return *shared->ddl_worker;
}
zkutil::ZooKeeperPtr Context::getZooKeeper() const