[RelEng] Simplify creation of release P2 repo and restore its mirrorsURL#3204

HannesWell merged 1 commit intoeclipse-platform:mastereclipse-platform/eclipse.platform.releng.aggregator:masterfrom

HannesWell:ensure-p2.mirrorsURLHannesWell/eclipse.platform.releng.aggregator:ensure-p2.mirrorsURLCopy head branch name to clipboard