Fixes for 'backup.pl' (Bug #11816)

Fixes for 'backup.pl' (Bug #11816)

Hi,

Fixes #11816
(https://bugzilla.ipfire.org/show_bug.cgi?id=11816 and
https://bugzilla.ipfire.org/attachment.cgi?id=608):

"[root@ipfire ~]# backupctrl exclude
...
tar: The following options were used after any non-optional arguments in
archive create or update mode.  These options are positional and affect
only arguments that follow them.  Please, rearrange them properly.
tar: --exclude-from '/var/ipfire/backup/exclude.user' has no effect
tar: Exiting with failure status due to previous errors"

Please test - I got no errors anymore.

Best,
Matthias

Signed-off-by: Matthias Fischer <matthias.fischer@ipfire.org>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>