**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 try_assign_merge = [&](const String & partition_id) -> bool
    {
        constexpr size_t max_retries = 10;
        size_t try_no = 0;
        for (; try_no < max_retries; ++try_no)
        {
            
            
            std::lock_guard merge_selecting_lock(merge_selecting_mutex);
            ReplicatedMergeTreeMergePredicate can_merge = queue.getMergePredicate(zookeeper);
            auto future_merged_part = std::make_shared<FutureMergedMutatedPart>();
            if (storage_settings.get()->assign_part_uuids)
                future_merged_part->uuid = UUIDHelpers::generateV4();
            constexpr const char * unknown_disable_reason = "unknown reason";
            String disable_reason = unknown_disable_reason;
            SelectPartsDecision select_decision = SelectPartsDecision::CANNOT_SELECT;
            if (partition_id.empty())
            {
                select_decision = merger_mutator.selectPartsToMerge(
                    future_merged_part,  true, storage_settings_ptr->max_bytes_to_merge_at_max_space_in_pool,
                    can_merge,  false, &disable_reason);
            }
            else
            {
                select_decision = merger_mutator.selectAllPartsToMergeWithinPartition(
                    future_merged_part, disk_space, can_merge, partition_id, final, metadata_snapshot,
                    &disable_reason, query_context->getSettingsRef().optimize_skip_merged_partitions);
            }
            
            if (select_decision == SelectPartsDecision::NOTHING_TO_MERGE)