Switch to using Hiera data in the module instead of accessing variables in another scope

[ghoneycutt]

Currently the code accesses variables in other scopes, such as $sensu::owner and $sensu::group. Instead that data should be refactored to use Hiera.

https://docs.puppet.com/puppet/4.10/hiera_migrate_modules.html#module-data-with-yaml-data-files

[ghoneycutt]

Closing because it requires puppet >= 4.9. We've got some time before that's acceptable.