ids-functions.pl: Rework function write_modify_sids_file().
Directly implement the logic to determine the used ruleset and if
IDS or IPS mode should be used into the function instead of pass those
details as arguments.
This helps to prevent from doing this stuff at several places again and again.
Signed-off-by: Stefan Schantl <stefan.schantl@ipfire.org> Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>