Merge pull request #59792 from juju-solutions/bug/basicmaster

Automatic merge from submit-queue (batch tested with PRs 59788, 59846, 59792). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

 Juju deployments change basic auth password should keep admin in masters group

**What this PR does / why we need it**: This is a bug fix for juju k8s deployments. Re-configuring client_password should keep the admin user on the masters group. 

**Which issue(s) this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close the issue(s) when PR gets merged)*:
Fixes #

**Special notes for your reviewer**:

**Release note**:

```release-note
NONE
```

cluster/juju/layers/kubernetes-master/reactive/kubernetes_master.py

@@ -270,7 +270,7 @@ def password_changed():
     elif password == "":
         # Password not initialised
         password = token_generator()
-    setup_basic_auth(password, "admin", "admin")
+    setup_basic_auth(password, "admin", "admin", "system:masters")
     set_state('reconfigure.authentication.setup')
     remove_state('authentication.setup')
     set_state('client.password.initialised')