Enable IPv6 reachability check override

Setting the policy to true overrides the IPv6 reachability check. This means that the system will always query AAAA records when resolving host names. It applies to all users and interfaces on the device. Setting the policy to false or leaving it unset does not overrides the IPv6 reachability check. The system only queries AAAA records when it is reachable to a global IPv6 host.