Merge pull request #48351 from juju-solutions/bug/get-pass

Automatic merge from submit-queue (batch tested with PRs 48317, 48313, 48351, 48357, 48115)

Ensure get_password is accessing a file that exists.

**What this PR does / why we need it**: get_password will throw an exception instead of returning None in case the basic_auth.csv file is missing but /root/cdk/ is there in a juju deployment.

**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes https://github.com/juju-solutions/bundle-canonical-kubernetes/issues/324

**Special notes for your reviewer**:

**Release note**:

```
Fix race condition where /root/cdk is not yet initialised in kubernetes-master setup by Juju  
```

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

@@ -920,9 +920,9 @@ def setup_tokens(token, username, user):
 def get_password(csv_fname, user):
     '''Get the password of user within the csv file provided.'''
     root_cdk = '/root/cdk'
-    if not os.path.isdir(root_cdk):
-        return None
     tokens_fname = os.path.join(root_cdk, csv_fname)
+    if not os.path.isfile(tokens_fname):
+        return None
     with open(tokens_fname, 'r') as stream:
         for line in stream:
             record = line.split(',')