Update docker.rb for Podman

[adamboutcher]

Summary

This if statement will enable the fact to work if you are using podman with docker symlink/support as the json syntax is lowercase on podman but camel/title case on docker.

Related Issues (if any)

https://github.com/puppetlabs/puppetlabs-docker/issues/982 Possibly this too https://github.com/puppetlabs/puppetlabs-docker/issues/749

Provide a detailed description of all the changes present in this pull request. Just an if statement in the factor code (docker.rb)

Checklist

• [ ] 🟢 Spec tests.
• [ ] 🟢 Acceptance tests.
• [X] Manually verified. (For example puppet apply)

[CLAassistant]

All committers have signed the CLA.

[Henrik-Hansson]

Hi @torgeiou anything missing? I can try to help out in that case.