install-chef-suse: Create a /etc/chef/client.rb file on admin server

We don't have this file, and this creates some warnings/errors:

```
[Mon, 04 Aug 2014 15:24:34 +0200] WARN: *****************************************
[Mon, 04 Aug 2014 15:24:34 +0200] WARN: Did not find config file: /etc/chef/client.rb, using command line options.
[Mon, 04 Aug 2014 15:24:34 +0200] WARN: *****************************************
[...]
[Mon, 04 Aug 2014 15:24:35 +0200] INFO: HTTP Request Returned 404 Not Found: No routes match the request: /reports/nodes/crowbar.site/runs
```

It's trivial to have the minimal config bits that are required to avoid
these.

(Note that we disable reporting as it requires Chef Enterprise)