**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.

{
    auto ptr = session_context.lock();
    if (!ptr) throw Exception("There is no session or session context has expired", ErrorCodes::THERE_IS_NO_SESSION);
    return ptr;
}
ContextMutablePtr Context::getGlobalContext() const
{
    auto ptr = global_context.lock();
    if (!ptr) throw Exception("There is no global context or global context has expired", ErrorCodes::LOGICAL_ERROR);
    return ptr;
}
ContextMutablePtr Context::getBufferContext() const
{
    if (!buffer_context) throw Exception("There is no buffer context", ErrorCodes::LOGICAL_ERROR);
    return buffer_context;
}
const EmbeddedDictionaries & Context::getEmbeddedDictionaries() const
{
    return getEmbeddedDictionariesImpl(false);
}
EmbeddedDictionaries & Context::getEmbeddedDictionaries()
{
    return getEmbeddedDictionariesImpl(false);
}
const ExternalDictionariesLoader & Context::getExternalDictionariesLoader() const
{
    return const_cast<Context *>(this)->getExternalDictionariesLoader();
}
ExternalDictionariesLoader & Context::getExternalDictionariesLoader()