CVE-2022-37966 param: don't explicitly initialize "kdc force enable rc4 weak session keys" to false/"no"

This is not squashed in order to allow easier backports...

BUG: https://bugzilla.samba.org/show_bug.cgi?id=15237

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Joseph Sutton <josephsutton@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
