Wrong exit code when server is not reachable

## Expected behavior

```bash
$ vagrant provision dev
==> dev: The managed server is not reachable. Check if the `config.managed.server` is correct.
$ echo $?
1
```

## Actual behavior

```bash
$ vagrant provision dev
==> dev: The managed server is not reachable. Check if the `config.managed.server` is correct.
$ echo $?
0
```
