Fix for bug 12539

Fix for bug 12539

The installer recognises cups and cups-filters both as cups and puts
two instances of cups in the add-on services table.
Based on input from Michael Tremer this patch replaces the command
returning the second element between hyphens with one that takes
what comes after "meta-" using Perl code rather than a shell command.
The second find command was changed as per Michael's suggestion.

Tested in my ipfire test bed system and only results in one cups
entry.
Signed-off-by: Adolf Belka <ahb.ipfire@gmail.com>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>