[RM-2332] Check permissions for some stores and subjects. Records the user to last configure a backup builder, and subsequently runs as that person.
Option to not back up master.key (or identity.key).
[RM-2049] Mostly reverted prior fix, which did not work anyway. Simply do not back up tool installer caches.
/var/jenkins_backup is considered invalid backup location as it "startsWith" /var/jenkins