[JENKINS-49340] Be able to mark a job as succesful even if it has failing tests

I'm using withMaven and running maven in a pipeline. withMaven junit publisher sets the build as UNSTABLE when there's a test.

However we check for flakey tests and when only flakey tests are found, we'd like to mark the job as sucessful. We tried doing this (see https://github.com/xwiki/xwiki-jenkins-pipeline/blob/master/vars/xwikiBuild.groovy#L230) but the job is still reported as failing in the Jenkins UI and in the logs.

Jenkins