Fix deprecation message regarding concat::setup
Unbreak OpenBSD support
Error: invalid byte sequence in US-ASCII
Adjust service handling for OpenBSD

- OpenBSD has support for rc scripts for several years now, and Puppet supports
it for some time too now. However the service name is 'munin_node' instead of
'munin-node' so adjust for that.
Use better $group on OpenBSD
- use a cron{} resource as cron.d doesn't exist on OpenBSD
- 'munin-server' is the name of the package on OpenBSD