avoid shadowing in augeas state

```
************* Module salt.states.augeas
salt/states/augeas.py:177: [W0622(redefined-builtin), change] Redefining built-in 'file'
salt/states/augeas.py:223: [W0621(redefined-outer-name), setvalue] Redefining name 'change' from outer scope (line 42)
```