Convert Hiera configuration file to v5

gloprequested to merge
glop/puppet:fix/hiera-yaml-v5 into master

Hello!

The Hiera 3 format is now deprecated and generates a warning:

Warning: /etc/puppet/hiera.yaml: Use of 'hiera.yaml' version 3 is deprecated. It should be converted to version 5
   (file: /etc/puppet/hiera.yaml)

I've basically followed the Puppet 5.5 documentation in order to convert this file to Hiera 5 while keeping the same hierarchy as in its v3 version.

Thank you!

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