On a busy Red Hat Satellite6 , online backup fails with errors due to changing files

Issue

• During the course of a Red Hat Satellite backup using the foreman-maintain tool, the backup can fail with errors about tar being unable to gather certain files because they've been removed since the backup started.

  # backupdir=/tmp/backup/ ; foreman-maintain backup online --assumeyes --skip-pulp-content $backupdir
  (output truncated)
  tar: /var/lib/candlepin/activemq-artemis/journal/activemq-data-7.amq: file changed as we read it
  tar: /var/lib/qpidd/.qpidd/qls/p001/efp/2048k/in_use/3UUID.jrnl: File removed before we read it
  tar: /var/lib/qpidd/.qpidd/qls/p001/efp/2048k/in_use/UUID.jrnl: File removed before we read it
  

  Additional info: This is similar to the specific situation encountered in https://access.redhat.com/solutions/3108771