**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("zookeeper");
}
bool Context::hasAuxiliaryZooKeeper(const String & name) const
{
    return getConfigRef().has("auxiliary_zookeepers." + name);
}
InterserverCredentialsPtr Context::getInterserverCredentials()
{
    return shared->interserver_io_credentials.get();
}
void Context::updateInterserverCredentials(const Poco::Util::AbstractConfiguration & config)
{
    auto credentials = InterserverCredentials::make(config, "interserver_http_credentials");
    shared->interserver_io_credentials.set(std::move(credentials));
}
void Context::setInterserverIOAddress(const String & host, UInt16 port)
{
    shared->interserver_io_host = host;
    shared->interserver_io_port = port;
}
std::pair<String, UInt16> Context::getInterserverIOAddress() const
{
    if (shared->interserver_io_host.empty() || shared->interserver_io_port == 0)
        throw Exception("Parameter 'interserver_http(s)_port' required for replication is not specified in configuration file.",
                        ErrorCodes::NO_ELEMENTS_IN_CONFIG);
    return { shared->interserver_io_host, shared->interserver_io_port };
}
void Context::setInterserverScheme(const String & scheme)