(PUP-2578) Adjustments for new OpenBSD service provider

After some more testing of @xaque208 new service provider I ran into an issue where a service from packages like:

    service {'puppetboard':
      enable => true
    }

would end up with the following in `/etc/rc.conf.local`:

    puppetboard_flags=""

This breaks the script, as it has sets it's local `daemon_flags` which are then overridden by the flags from `rc.conf.local` (to `""`), so if there are no `:flags` set, then the `_flags=""` should not be written out.

Also, order is important for `pkg_scripts` as things like avahi-daemon need dbus_daemon to be started. Therefore `pkg_scripts` must not be sorted but just append to and let people define the order (if there needs to be one) by using dependency resources.

Thirdly, after some discussion it was deemed better (and faster) to turn `#in_base?` really into "in base" instead of "not in base" by looking at `/etc/rc.conf` which contains all the base daemons.
For my own curiosity, why are empty flags still written out but only for base services?  If I specify `flags => ""` for the resource, but the service isn't base, it is ignored?

I'm not a OpenBSD user, so I completely acknowledge my ignorance here, but at a cursory glance it seems like `append = resource[:name] + '_flags="' + flags + '"' if flags` would suffice instead of the if/else, to me at least.