pin redisio version

When running the latest on prod, I got:

```
Chef::Exceptions::RecipeNotFound
--------------------------------
could not find recipe configure for cookbook redisio
```

This is because we were using 2.X of the redisio cookbook in test kitchen, but it's pinned to 1.7.1 in prod. This pins it to 1.7.1 in this cookbook's Berkshelf so Test Kitchen runs use the same version we use in prod.