Drop empty yaml file
Drop empty yaml file

Empty yaml files in hiera produce a puppetserver log.

```
Puppet /mnt/puppetnfsdir/environments/production/modules/yum/data/os/RedHat.yaml: file does not contain a valid yaml hash
```

There is some background on this here:

* https://tickets.puppetlabs.com/browse/PUP-7414

voxpupuli/puppet-yum