[fix] handling of true objects

[Nokius]

This PR covers the fix to solve #42.

The PR contains:

• fix for templates/object_attributes.j2 to handle true values correct
• Update to guide users to use ApiListener (current one turns into a faulty config)

[martialblog]

Hi, This role is no longer maintained. See: https://github.com/Icinga/ansible-collection-icinga