Optaplanner promote pipeline should catch error on `Reset quickstarts branch`

https://github.com/kiegroup/optaplanner/blob/master/Jenkinsfile.promote#L124

This should use https://www.jenkins.io/doc/pipeline/steps/workflow-basic-steps/#catcherror-catch-error-and-set-build-result-to-failure and set the stage and job result as UNSTABLE, so it does not block the pipeline for further action

If that stage fails then the action will be done manually