More secure default server setting

[binford2k]

Under some fairly obscure conditions, defaulting the server setting to
'puppet' can be a security concern. Because the worst case scenario
involves a user accidentally running puppet agent -t on an untrusted
network, this PR removes the default completely when non-root.
Otherwise, it just prints a deprecation warning.

Fixes https://github.com/voxpupuli/security-tracking/issues/22

[binford2k]

fwiw, I'm not actually happy with this solution. It means that in a completely serverless workflow, you'll have spurious warnings in the logs like such. I'll try to find a better way later, after we decide if this is a good idea or not.

$ sudo puppet apply /tmp/site.pp
Warning: OpenVox will not default to `server=puppet` as of version 9.0. Please update your configuration appropriately.
   (location: /opt/puppetlabs/puppet/lib/ruby/vendor_ruby/puppet/defaults.rb:1659:in `block in initialize_default_settings!')
Notice: Compiled catalog for lilith.local in environment production in 0.00 seconds
...

[binford2k]

I moved the check and warnings to the http service so it only screams if you actually use it. This avoids, for example, the spurious deprecation message when running puppet apply, or even puppet config set to set it in the first place!