Add fact sets for SLES15

[rodjek]

/cc puppetlabs/pdk#711

[coveralls]

Coverage remained the same at 100.0% when pulling 84f2037 on rodjek:sles-15 into 96ec245 on camptocamp:master.

[baurmatt]

Hey @rodjek,

I just stumbled over a problem with this change. Some of the newly introduced facts sets don't have a "operatingsystem" fact. In particular those are:

• 2.2
• 2.3
• 2.4
• 2.5

This leads to problem with rspec-puppet-facts-unsupported.

I'm not 100% sure, but shouldn't every fact set (especially for a "enterprise" OS as this one) have a "operatingsystem" fact?

[rodjek]

They don't have an operatingsystem fact because Facter 2.x doesn't return one for SLES15. This is the behaviour of Facter 2.x on that distro, so I think FacterDB should show this and rspec-puppet-facts-unsupported should be updated to not assume the presence of this fact.