Changes

Jenkins recipe helpers - detect UPSTREAM_VERSION again

* jenkins-core-*/check-version.sh: adapt to markup changes of https://get.jenkins.io/ directory listing to detect newest UPSTREAM_VERSION properly again

* jenkins-core-*/check-version.sh: we always print how to commit the change, even if there is none - clarify "if needed"

It is possible that a local workspace has the Makefiles updated,
but commit was not yet made, so suggestion is useful.
 (commit: 382c2ea)