This is a follow-up to https://github.com/jenkinsci/ci.jenkins.io-runner/pull/68 and https://github.com/jenkinsci/ci.jenkins.io-runner/issue/67 . The root cause of these issues is that plugins from pom.xml are being incorrectly resolved and cached as non-plugins if settings.xml does not refer a server with Jenkins plugins

Acceptance criteria:

• Caching logic is updated to be inconclusive when artifact directory is missing (no metadata file). On new runs the resolution should be re-attempted
• Negative value should be cached if and only if the artifact directory exists but there is no HPI artifact