Setting JupyterHub.admin_access does not change anything

Bug description

By default, accessing other user Servers should be disabled. This is not the case. If I comment out the line in the config, so that it is set to False, its still possible to access user servers. Yes, I saved the config and restarted the Hub. Standard Installation without changes.

Expected behaviour

Access to other servers is denied

Actual behaviour

Access is always possible if you are admin

How to reproduce

try to set the setting in the config

Go to '...'
Click on '....'
Scroll down to '....'
See error

Your personal set up

Standard Installation using QuickStart. Ubuntu 20.04 LTS VM, 16 GB Ram, 8 vCPUs. Using default spawner and authenticator. Version 2.3.0. If you need more information, please ask.

Full environment

``` alembic==1.7.7 anyio==3.5.0 argon2-cffi==21.3.0 argon2-cffi-bindings==21.2.0 asttokens==2.0.5 async-generator==1.10 attrs==19.3.0 Automat==0.8.0 Babel==2.10.1 backcall==0.2.0 beautifulsoup4==4.11.1 bleach==5.0.0 blinker==1.4 certifi==2019.11.28 certipy==0.1.3 cffi==1.15.0 chardet==3.0.4 Click==7.0 cloud-init==22.1 colorama==0.4.3 command-not-found==0.3 configobj==5.0.6 constantly==15.1.0 cryptography==2.8 dbus-python==1.2.16 debugpy==1.6.0 decorator==5.1.1 defusedxml==0.7.1 distro==1.4.0 distro-info===0.23ubuntu1 entrypoints==0.3 executing==0.8.3 fastjsonschema==2.15.3 greenlet==1.1.2 httplib2==0.14.0 hyperlink==19.0.0 idna==2.8 importlib-metadata==4.11.3 importlib-resources==5.7.1 incremental==16.10.1 ipykernel==6.13.0 ipython==8.3.0 ipython-genutils==0.2.0 jedi==0.18.1 Jinja2==3.1.2 json5==0.9.8 jsonpatch==1.22 jsonpointer==2.0 jsonschema==3.2.0 jupyter-client==7.3.1 jupyter-core==4.10.0 jupyter-server==1.17.0 jupyter-telemetry==0.1.0 jupyterhub==2.3.0 jupyterlab==3.4.0 jupyterlab-pygments==0.2.2 jupyterlab-server==2.13.0 keyring==18.0.1 language-selector==0.1 launchpadlib==1.10.13 lazr.restfulclient==0.14.2 lazr.uri==1.0.3 Mako==1.2.0 MarkupSafe==2.1.1 matplotlib-inline==0.1.3 mistune==0.8.4 more-itertools==4.2.0 nbclassic==0.3.7 nbclient==0.6.3 nbconvert==6.5.0 nbformat==5.4.0 nest-asyncio==1.5.5 netifaces==0.10.4 notebook==6.4.11 notebook-shim==0.1.0 oauthlib==3.1.0 packaging==21.3 pamela==1.0.0 pandocfilters==1.5.0 parso==0.8.3 pexpect==4.6.0 pickleshare==0.7.5 prometheus-client==0.14.1 prompt-toolkit==3.0.29 psutil==5.9.0 ptyprocess==0.7.0 pure-eval==0.2.2 pyasn1==0.4.2 pyasn1-modules==0.2.1 pycparser==2.21 Pygments==2.12.0 PyGObject==3.36.0 PyHamcrest==1.9.0 PyJWT==1.7.1 pymacaroons==0.13.0 PyNaCl==1.3.0 pyOpenSSL==19.0.0 pyparsing==3.0.9 pyrsistent==0.15.5 pyserial==3.4 python-apt==2.0.0+ubuntu0.20.4.7 python-dateutil==2.8.2 python-debian===0.1.36ubuntu1 python-json-logger==2.0.2 pytz==2022.1 PyYAML==5.3.1 pyzmq==22.3.0 requests==2.22.0 requests-unixsocket==0.2.0 ruamel.yaml==0.17.21 ruamel.yaml.clib==0.2.6 SecretStorage==2.3.1 Send2Trash==1.8.0 service-identity==18.1.0 simplejson==3.16.0 six==1.14.0 sniffio==1.2.0 sos==4.3 soupsieve==2.3.2.post1 SQLAlchemy==1.4.36 ssh-import-id==5.10 stack-data==0.2.0 systemd-python==234 terminado==0.13.3 tinycss2==1.1.1 tornado==6.1 traitlets==5.2.0 Twisted==18.9.0 ubuntu-advantage-tools==27.7 ufw==0.36 unattended-upgrades==0.1 urllib3==1.25.8 wadllib==1.3.3 wcwidth==0.2.5 webencodings==0.5.1 websocket-client==1.3.2 zipp==3.8.0 zope.interface==4.7.1 ```

Configuration

```python # c.LocalAuthenticator.create_system_users = True c.JupyterHub.admin_access = False c.Authenticator.admin_users = {'tim'} ```

Logs

``` # paste relevant logs here, if any ```

jupyterhub / jupyterhub