(SUP-2557) Ensure backup class is not included by default

[m0dular]

Prior to this commit, by default the pe_databases::backup class would be
included but not do anything. That was because the logic for the class
parameter was correct

disable_maintenance => ! $manage_database_backups

But the logic to include the class was not

if defined('$manage_database_backups')

This commit fixes this logic and adds spec tests to cover it. I also
moved the test for checking the cron resources from an acceptance test
to spec.

[puppet-community-rangefinder]

pe_databases is a class

that may have no external impact to Forge modules.

This module is declared in 0 of 578 indexed public Puppetfiles.

---

These results were generated with Rangefinder, a tool that helps predict the downstream impact of breaking changes to elements used in Puppet modules. You can run this on the command line to get a full report.

Exact matches are those that we can positively identify via namespace and the declaring modules' metadata. Non-namespaced items, such as Puppet 3.x functions, will always be reported as near matches only.

[jarretlavallee]

LGTM