/mnt/jenkins-tmp was a live hack to get a tmpfs system on gallium. It has been replaced by /var/lib/jenkins/tmpfs which is now used by the ant script.
Let a few days flow in to make sure it is no more needed. If the /mnt/jenkins-tmp is still empty by that time, we can remove the mount entry in fstab, unmount and remove the mount point.
Version: unspecified
Severity: trivial