Fix package downgrading for non-{RedHat,Debian} systems

[amotl]

Dear @adamantike,

thank you very much for your report at #346:

Root cause is #336, as the introduced parameter allow_downgrade is not supported by the pacman manager module, so that using Ansible >= 2.12 on Arch Linux would croak like:

Unsupported parameters for (ansible.legacy.pacman) module: allow_downgrade.

I feel responsible for that regression, because I just had focussed on Debian and apparently completely missed the big picture. Apologies.

I am submitting this patch to improve the situation as a draft, because I haven't been able to test it hands-on yet. Do you think it would resolve the issue for you? Apparently, as the software tests seem to succeed, can I humbly ask you to give it a try and report back about the outcome?

In order to pull the patched recipe directly from the git repository, you would put something along those lines into your requirements.yaml file.

roles:
  - name: ansible-role-docker
    src: git+https://github.com/crate-workbench/ansible-role-docker.git
    version: "amo/allow-downgrades-debian-redhat-only"

With kind regards, Andreas.

[RealOrangeOne]

Tested working correctly with ansible 2.12.5:

TASK [geerlingguy.docker : Install Docker (Ansible <2.12).] *********************************************************************************************
ok: [xxxx]

TASK [geerlingguy.docker : Install Docker (Ansible >=2.12).] ********************************************************************************************
skipping: [xxxx]

Clearly picks the <2.12 version

[amotl]

Dear Jeff,

I know your time is scarce. Can I still humbly ask you to bring in this patch and cut another release? It will fix #346, so the Arch Linux users from the community, like @adamantike and @RealOrangeOne, will be grateful.

Thank you very much in advance for taking the time and apologies for the hiccup introduced by my recent patch #336.

With kind regards, Andreas.

[amotl]

Thank you very much!