**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.

{
    std::lock_guard lock(shared->clusters_mutex);
    if (!shared->clusters)
        throw Exception("Clusters are not set", ErrorCodes::LOGICAL_ERROR);
    shared->clusters->setCluster(cluster_name, cluster);
}
void Context::initializeSystemLogs()
{
    auto lock = getLock();
    shared->system_logs = std::make_unique<SystemLogs>(getGlobalContext(), getConfigRef());
}
void Context::initializeTraceCollector()
{
    shared->initializeTraceCollector(getTraceLog());
}
bool Context::hasTraceCollector() const
{
    return shared->hasTraceCollector();
}
std::shared_ptr<QueryLog> Context::getQueryLog() const
{
    auto lock = getLock();
    if (!shared->system_logs)
        return {};
    return shared->system_logs->query_log;
}
std::shared_ptr<QueryThreadLog> Context::getQueryThreadLog() const