(Maint) Create spec coverage for parser face

The parser face had no spec test coverage. This creates some coverage
around the code. This coverage replaces what is currently being done in
an acceptance test.
Merge pull request #1955 from zaphod42/maint/master/improve-coverage-of-parser-validate

(Maint) Create spec coverage for parser face
Merge branch 'master' of https://github.com/puppetlabs/puppet