check-backups.sh now check the status of the backup script

[dwlfrth]

Added a check in check-backups.sh for the output value of the database backup script.

Do not merge before merging inverse-inc/packetfence#1904

Take note of the "require root" attribute that was already present in this script. We may want to discuss this since the check won't run if do not have root permission even if that part of the check does not require root permissions.

Also, take note that PacketFence setups running a previous database-backup-and-maintenance script will throw an error.

[julsemaan]

The thing with this PR is that it will fail unless the db maintenance script is updated but there is no check for an available update. Even worse, the update check can't apply to this as that script is often modified.

We can either:

• Only exit fail if the file isn't there and the version is higher than 6.5 (which will have the updated script)
• Not exit-fail if the backup status isn't there

[julsemaan]

problematic around status file existance

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