nfs: update refs

Fix travis
Merge pull request #725 from enovance/update_refs_nfs

nfs: update refs
(rspec) Nfs: Fix puppet-module-nfs sha

* The previous commit broke rspec tests.
* Refs: #717 #725
* See: https://github.com/enovance/puppet-module-nfs/commit/eced57eeedc55e30e8e1dd18332e192855f5f396
Merge pull request #726 from enovance/fix-rspec

(rspec) Nfs: Fix puppet-module-nfs sha
Delete .fixtures.yml files and use librarian-puppet-simple

Using librarian-puppet-simple to read Puppetfile for your rspec-puppet
fixtures.