Scenario 1:  no permission configuration

Result: The RBAC tab is visible with no records listed

Scenario 2:  with permission configured but enabled is set to `false` :
```

permission:
  enabled: false
   rbac:
      policies-csv-file: /Users/dsantra/Downloads/backstage-plugins/rbac-policy.csv
      policyFileReload: true
      pluginsWithPermission:
        - kubernetes
        - jenkins
      admin:
         users:
          # - name: user:default/debsmita1
          - name: group:default/admins
```
 
Result: The RBAC tab is visible with records listed

with the above configuration, when logged in as `debsmita1` , RBAC page is shown because the permission backend says that the user is authorized to view the page

Expectation: The RBAC tab is visible only when RBAC plugin is enabled and logged in user is authorized to list roles.