Use product version in reference label

[deneb-alpha]

What does this PR change?

The reference label value needs to match the build tag and then contain the product version.

The ARG PRODUCT_VERSION is appended when pushing the image to OBS.

Links

Issue(s): https://github.com/SUSE/spacewalk/issues/22011

Changelogs

Make sure the changelogs entries you are adding are compliant with https://github.com/uyuni-project/uyuni/wiki/Contributing#changelogs and https://github.com/uyuni-project/uyuni/wiki/Contributing#uyuni-projectuyuni-repository

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• No changelog needed

If you uncheck the checkbox after the PR is created, you will need to re-run changelog_test (see below)

Re-run a test

If you need to re-run a test, please mark the related checkbox, it will be unchecked automatically once it has re-run:

• Re-run test "changelog_test"
• Re-run test "backend_unittests_pgsql"
• Re-run test "java_pgsql_tests"
• Re-run test "schema_migration_test_pgsql"
• Re-run test "susemanager_unittests"
• Re-run test "javascript_lint"
• Re-run test "spacecmd_unittests"

Before you merge

Check How to branch and merge properly!

[deneb-alpha]

@cedric added this change in #8144 closing this PR