- load sysctls earlier (bnc#664550)
- move distro defaults to /lib/sysctl.d to avoid .rpmnew files
- enable IPv6 privacy by default (bnc#678066)

I've sent the --system and --pattern path upstream but they weren't accepted
yet. So this is tentative but we need the /lib/sysctl.d feature to be able to
provide distro defaults in a sane way.