Add spec coverage of parser configuration

Without this patch we don't have any spec coverage of the change being
made.  This patch adds a single test that makes sure the setup_puppet
method reads the parser configuration from itself.  We don't actually
test to make sure the configuration is read from Rspec, but the majority
of the behavior in the method is covered.

We also aren't testing that the setting is actually written to Puppet
since mocking the :[]= method is non-trivial when called many times in
single method invocation.