Module ''ceph_add_users_buckets.py" is not idempotent - Simple update could fix it

The module lack idempotency as it's important for ansible , it simply need not to consider existing users/buckets as error .
To do that simply do not raise `module.fail_json` and instead put change false to the result dict in the main function:

```
# conditional state caused a failure
if result['added_users'] == '' and result['added_buckets'] == '':
#module.fail_json(msg='No users or buckets were added successfully' , **result)
result['changed'] = False
# EXIT
module.exit_json(**result)

if __name__ == '__main__':
main()
```

Open ceph_add_users_buckets.py and inspect the main function around the conditional state check and module.fail_json call. Preserve the result and finish through module.exit_json; done means existing users or buckets no longer cause an error and the result reports changed as false.

Written by the indexing model from the issue text.