**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.

{
        case LogEntry::ATTACH_PART:
            
            [[fallthrough]];
        case LogEntry::GET_PART:
            return executeFetch(entry);
            
        case LogEntry::MERGE_PARTS:
            throw Exception(ErrorCodes::LOGICAL_ERROR, "Merge has to be executed by another function");
        case LogEntry::MUTATE_PART:
            throw Exception(ErrorCodes::LOGICAL_ERROR, "Mutation has to be executed by another function");
        case LogEntry::ALTER_METADATA:
            return executeMetadataAlter(entry);
        case LogEntry::SYNC_PINNED_PART_UUIDS:
            syncPinnedPartUUIDs();
            return true;
        case LogEntry::CLONE_PART_FROM_SHARD:
            executeClonePartFromShard(entry);
            return true;
        default:
            throw Exception(ErrorCodes::LOGICAL_ERROR, "Unexpected log entry type: {}", static_cast<int>(entry.type));
    }
    
}
bool StorageReplicatedMergeTree::executeFetch(LogEntry & entry)
{
    
    String replica = findReplicaHavingCoveringPart(entry, true);
    const auto storage_settings_ptr = getSettings();
    auto metadata_snapshot = getInMemoryMetadataPtr();