Fix api changes

Due to recent changes in fleet our client was broken.

### changes
- it is no longer possible to fetch a `Job` object
- now there are `Unit` and `Scheduled` objects available, each with different properties
- all states now needs to be fetched at once, one needs to pick the desired state
- simplified makefile, I got errors like the following

```bash
/fleet-client-go $ make
...
go install runtime: open /usr/local/go/pkg/linux_amd64/runtime.a: permission denied
...
```