Packages: Be able to assign instances via variable

[jrx]

Broken because of: ansible/ansible#9362

The following example is not possible:

- name: Ensure Marathon-LB is installed
  dcos_package:
    name: marathon-lb
    app_id: marathon-lb
    version: 1.12.2
    state: present
    options:
      marathon-lb:
        instances: "{{ groups['agents_public'] | length }}"

[a-nldisr]

Is this still relevant since the ansible/ansible#9362 has been resolved