avoid shadowing exists() func within aws_sqs state

```
salt/states/aws_sqs.py:52: [W0621(redefined-outer-name), exists] Redefining name 'exists' from outer scope (line 30)
salt/states/aws_sqs.py:95: [W0621(redefined-outer-name), absent] Redefining name 'exists' from outer scope (line 30)
```