Added an option to disable a backup job while preserving its
settings. When a job is disabled a '#' is added in front of the vzdump
command in the vzdump.cron file. So the cron job still fires,
but only a comment gets executed. If we would comment out the cron job
a bit more changes to the parser would be needed.
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>