Error message during Rear backup with rsync: failed to write xattr user.rsync.%stat for <file> Operation not permitted

Issue

• During a Rear backup configured with rsync method with user other than root, we get this kind of error messages:

  rsync: failed to write xattr user.rsync.%stat for "/srv/backup/var/lib/gssproxy/default.sock": Operation not permitted (1)
  rsync: failed to write xattr user.rsync.%stat for "/srv/backup/var/spool/postfix/private/anvil": Operation not permitted (1)
  rsync: failed to write xattr user.rsync.%stat for "/srv/backup/var/spool/postfix/private/bounce": Operation not permitted (1)
  rsync: failed to write xattr user.rsync.%stat for "/srv/backup/var/spool/postfix/private/defer": Operation not permitted (1)
  rsync: failed to write xattr user.rsync.%stat for "/srv/backup/var/spool/postfix/private/discard": Operation not permitted (1)
  rsync: failed to write xattr user.rsync.%stat for "/srv/backup/var/spool/postfix/private/error": Operation not permitted (1)