Add puppet_server fact to return agent's server
Add puppet_server fact to return agent's server

It is frequently useful to configure an agent to retrieve a resource
from it's configured master, or make further configuration adjustments
to itself based on what server it's using. Similar to the rationale for
stdlib providing a puppet_vardir fact, this commit adds a puppet_server
fact.

Note that the closest equivalent available today is $settings::server,
which returns only the MASTER's configured server, not the AGENT's. This
makes $settings::server unreliable, and not useful in a multi-master
deployment or a deployment involving a load balancer.

fuel-infra/puppetlabs-stdlib,DavidS/puppetlabs-stdlib,HelenCampbell/puppetlabs-stdlib,jbondpdx/puppetlabs-stdlib,puppetlabs/puppetlabs-stdlib