Fix: Gitlab runner repository GPG key permission check by making keyring-path configurable

[IQNeoXen]

This PR fixes an issue introduced in #404. The Ensure Gitlab runner repository GPG key is readable by everyone Task is trying to check a file that might not exist, which causes the role to fail on fresh installations.

This PR makes the keyring-path that is checked configurable, but defaults to the path provided by the official gitlab-runner script mentioned in the GitLab Docs.

• Docs: Add the official GitLab repository
• Script: gitlab-runner/script.deb.sh

Fixes the fix for #397 ;)

[IQNeoXen]

I just realized this was fixed in #413 🤦
I still like this configurable variant more though.

[guenhter]

LGTM.

[guenhter]

Thx for this contribution. Having it configurable is definitely a good thing.

[gwarf]

FTR, I only installed and configured the runner with this Ansible role, didn't do any manual setup.
I just saw these issues in the upstream, so it seems the script may have had changes/issues.
Unfortunately, after some quick search, I haven't been able to find an authoritative repo with the source of the script to see if it got changed or if I really messed up from my side:

• https://gitlab.com/gitlab-org/gitlab-runner/-/issues/39087
• https://gitlab.com/gitlab-org/gitlab-runner/-/issues/38898

Sorry if it created some issues, and thanks for everyone working on keeping this role up-to-date and working :)

[IQNeoXen]

@gwarf no worries. I also searched for the scripts source and wasn't able to find it, not sure where GitLab is hiding that...