(#771) Set a default dummy ipaddress6 fact
(#771) Set a default dummy ipaddress6 fact

Puppet 6.9.0 started setting a `serverip6` server fact which is set
using the value of the `ipaddress6` fact. If the fact set(s) provided by
FacterDB don't have an `ipaddress6` fact set, then the normal Facter
fact will be resolved, which can result in Ruby trying to load Windows
only gems on Linux.

Fixes #771

puppetlabs/rspec-puppet,DavidS/rspec-puppet,rodjek/rspec-puppet