**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 lock = getLock();
    shared->bridge_commands.emplace_back(std::move(cmd));
}
IHostContextPtr & Context::getHostContext()
{
    return host_context;
}
const IHostContextPtr & Context::getHostContext() const
{
    return host_context;
}
std::shared_ptr<ActionLocksManager> Context::getActionLocksManager()
{
    auto lock = getLock();
    if (!shared->action_locks_manager)
        shared->action_locks_manager = std::make_shared<ActionLocksManager>(shared_from_this());
    return shared->action_locks_manager;
}
void Context::setExternalTablesInitializer(ExternalTablesInitializer && initializer)
{
    if (external_tables_initializer_callback)
        throw Exception("External tables initializer is already set", ErrorCodes::LOGICAL_ERROR);
    external_tables_initializer_callback = std::move(initializer);
}
void Context::initializeExternalTablesIfSet()