Fix ensure_packages

Flip "installed" and "present" in Function "ensure_packages".
Puppet-Type "package" defaults to "installed" and not to "present" (compare https://github.com/puppetlabs/puppet/blob/main/lib/puppet/type/package.rb#L148).
This Misconception lies in the Code since the most early Days.

With flipping these two Values, Rspec-Tests do not have to be adapted, when migrating from "package {}" to "ensure_packages()".