Fixed apt cache update

[wsmirnow]

Apt cache update was triggered by a notify. A notify handler is running at the end of the Ansible block. As this role is used as dependency for other roles (like elan.opencast_elasticsearch), the trigger will run to late.

Example:

- name: Deploy Elasticsearch
  hosts: elasticsearch
  roles:
    - elan.opencast_elasticsearch <-- The packages are located in an Opencast repository
                                      that is unknown on a clean system. Without an apt update
                                      performed so far, the role will fail.
    <-- triggers would run here

Apt cache should be updated by this role and not by others.

[wsmirnow]

The tests are failing due to broken molecule tests. This is handled by #5.