(PUP-2702) Change to unlimited caching as the default

The most effective and safe caching strategy for environments is
"unlimited" since it gives the user control over the resource utiliztion
of the master, provides a clear deployment point, and allows the master
to pick up any ruby code changes that are part of the new environment
code.
Merge pull request #2711 from zaphod42/feature/puppet-4/pup-2702-change-to-unlimited

(PUP-2702) Change to unlimited caching as the default