suricata: correct rule actions in IPS mode

suricata: correct rule actions in IPS mode

In IPS mode rule actions need to be have the action 'drop' for the
protection to work, however this is not appropriate for all rules.
Modify the generator for oinkmaster-modify-sids.conf to leave
rules with the action 'alert' here this is appropriate.  Also add
a script to be run on update to correct existing downloaded rules.

Fixes #12086

Signed-off-by: Tim FitzGeorge <ipfr@tfitzgeorge.me.uk>
Tested-by: Peter Müller <peter.mueller@ipfire.org>
Signed-off-by: Stefan Schantl <stefan.schantl@ipfire.org>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>