Fix hostname generation
Fix hostname generation

Prior to this edit, at runtime terraform could not parse the expression:

```
var.name + var.avahi-domain
```

since it tries to convert it to int:

```
2016/07/01 16:26:54 [WARN] mbologna inside interpolation E R R O R (*errors.errorString)(0xc82023a7f0)(__builtin_StringToInt: strconv.ParseInt: parsing "clisles12": invalid syntax in:
${coalesce(var.name + var.avahi-domain, openstack_compute_instance_v2.instance.id)})
2016/07/01 16:26:54 [TRACE] [walkApply] Exiting eval tree: module.clisles12.output.hostname
2016/07/01 16:26:54 [DEBUG] vertex root.root: walking
```

Unfortunately, terraform DOES NOT handle the error correctly (and thus it
suppresses it).

This edit builds the hostname string correctly.

moio/sumaform,MalloZup/sumaform,MalloZup/sumaform,moio/sumaform,MalloZup/sumaform,moio/sumaform,MalloZup/sumaform