examples/ubuntu/avahi_client: fix daemon detection

On trusty the `service status` command out doesn't contain "process":
```
$ service avahi-daemon status
avahi-daemon stop/waiting
$ sudo service avahi-daemon start
avahi-daemon start/running
$ service avahi-daemon status
avahi-daemon start/running
```

Change-Id: Id062c8f6ae47eb0a4bf411af6cd0575aef98b815
Reviewed-on: https://weave-review.googlesource.com/1096
Reviewed-by: Vitaly Buka <vitalybuka@google.com>
1 file changed
tree: 4f12a3662449ee4edba33de93696eb622f60860a
  1. libweave/