Fix automatic default value selection for ssh::server::service_ensure (Fixes saz#453)

[webcompas]

This Pull Request (PR) fixes the following issues

Fixes #453

[greatflyingsteve]

Huge +1 for this. We can't upgrade beyond 14.1.0 because in our use case, the "normal" ensure values are wildly insufficient: we want to specify a minimum version, and then let a patch process outside of Puppet upgrade beyond that version without Puppet/DNF forcing a downgrade (or us having to make a code change every time there's another package update). This means our ensure values are going to look like >=18.5.2, which yum/dnf are perfectly capable of understanding, but this module won't allow through (yet) as of v15.0.0.

[saz]

@webcompas Can you update REFERENCE.md?