Support Chef12

Refer to https://github.com/opscode/chef/issues/2558 for some additional backstory here, but the gist of it that starting in Chef 12, trying to make assertions against the some resources will toss a `Cannot find a provider for blah` message.

This change should be a backward compatible change that avoids that error on Chef 12. I ran the change through a converge and test cycle on Chef 12.0.0, 11.16.4, 10.26.0 and 10.14.0.