Fix per loop LoopvarExperiment

```
$ go build -gcflags=all=-d=loopvar=2  github.com/scaleway/terraform-provider-scaleway/v2/scaleway
# github.com/scaleway/terraform-provider-scaleway/v2/scaleway
scaleway/helpers_redis.go:158:10: loop variable ip now per-iteration, stack-allocated
```


https://go.dev/wiki/LoopvarExperiment#my-test-fails-with-the-change-how-can-i-debug-it