Published URL no longer activates unrelated features like per job messages and PR autoclose

With current implementation of GhprbBuilds.onCompleted, a missing published url also deactivates unrelated features like per job comments and PR autoclose. See https://github.com/jenkinsci/ghprb-plugin/blob/master/src/main/java/org/jenkinsci/plugins/ghprb/GhprbBuilds.java#L123

This PR makes them independent of a published url.