**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 SharedContextHolder(std::make_unique<ContextSharedPart>());
}
ContextMutablePtr Context::createCopy(const ContextPtr & other)
{
    return std::shared_ptr<Context>(new Context(*other));
}
ContextMutablePtr Context::createCopy(const ContextWeakPtr & other)
{
    auto ptr = other.lock();
    if (!ptr) throw Exception("Can't copy an expired context", ErrorCodes::LOGICAL_ERROR);
    return createCopy(ptr);
}
ContextMutablePtr Context::createCopy(const ContextMutablePtr & other)
{
    return createCopy(std::const_pointer_cast<const Context>(other));
}
Context::~Context() = default;
InterserverIOHandler & Context::getInterserverIOHandler() { return shared->interserver_io_handler; }
std::unique_lock<std::recursive_mutex> Context::getLock() const
{
    ProfileEvents::increment(ProfileEvents::ContextLock);
    CurrentMetrics::Increment increment{CurrentMetrics::ContextLockWait};
    return std::unique_lock(shared->mutex);
}
ProcessList & Context::getProcessList() { return shared->process_list; }
const ProcessList & Context::getProcessList() const { return shared->process_list; }
MergeList & Context::getMergeList() { return shared->merge_list; }
const MergeList & Context::getMergeList() const { return shared->merge_list; }