**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.

mutable std::recursive_mutex mutex;
    
    mutable std::mutex embedded_dictionaries_mutex;
    mutable std::mutex external_dictionaries_mutex;
    mutable std::mutex external_user_defined_executable_functions_mutex;
    mutable std::mutex external_models_mutex;
    
    
    
    mutable std::mutex storage_policies_mutex;
    
    mutable std::mutex zookeeper_mutex;
    mutable zkutil::ZooKeeperPtr zookeeper;                 
    ConfigurationPtr zookeeper_config;                      
#if USE_NURAFT
    mutable std::mutex keeper_dispatcher_mutex;
    mutable std::shared_ptr<KeeperDispatcher> keeper_dispatcher;
#endif
    mutable std::mutex auxiliary_zookeepers_mutex;
    mutable std::map<String, zkutil::ZooKeeperPtr> auxiliary_zookeepers;    
    ConfigurationPtr auxiliary_zookeepers_config;           
    String interserver_io_host;                             
    UInt16 interserver_io_port = 0;                         
    String interserver_scheme;                              
    MultiVersion<InterserverCredentials> interserver_io_credentials;
    String path;                                            
    String flags_path;                                      
    String user_files_path;                                 
    String dictionaries_lib_path;                           
    String user_scripts_path;