Fix existing tag detection in workflow

[jnoordsij]

What does this PR do?

Fix failing workflows for commits on master with existing tags.

Motivation

Currently the step Check if tag exists on the release job fails to detect existing tags, because it does not account for the prefix v added (by default) by the Tag release action. This causes any commits not updating the chart version to result in a failure on the release job, as the Tag release job will fail with message "Validation Failed: {"resource":"Release","code":"already_exists","field":"tag_name"}".

This PR explicitly adds the prefix to both stages, so that existing tag detection works properly.

See also succesful example run on my fork and currently failing run on master.

More

• Yes, I updated the tests accordingly
• Yes, I ran make test and all the tests passed

[charlie-haley]

Thanks for the PR! LGTM

[mloiseleur]

Interesting. Thanks @jnoordsij , it looks good !