exclude: Remove the urlfilter pl programs from a backup

exclude: Remove the urlfilter pl programs from a backup

- When dealing with the qos bug fix for backing up .pl programs I also then searched all
   the /var/ipfire directory tree looking for any other .pl files that were being backed
   up and found that there were two for the urlfilter.
- This patch adds the .pl files in the urlfilter/bin directory to the exclude list.
- In the same way as for the qos change the exclude addition also means that these files
   will not be restorewd from any earlier backup.
- Also tested and confirmed on a physical IPFire system.

Tested-by: Adolf Belka <adolf.belka@ipfire.org>
Signed-off-by: Adolf Belka <adolf.belka@ipfire.org>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>