IPv6: privacy extension not active

From: https://discuss.freedombox.org/t/ipv6-privacy-extension-not-activated-by-default/1203

By user: ds11 (Nov '20)

On my freedombox ipv6 privacy extensions where not activated by default. This should be changed to avoid mac address leakage.

-> https://superuser.com/questions/243669/how-to-avoid-exposing-my-mac-address-when-using-ipv6