For ZDB namespaces, disable forwarding in the namespace

[delandtj]

When creating a namespace that hosts only a workload, i.e. the namespace is not used as some form of router but is only an edge,
forwarding needs to be disabled in the namespace.
https://github.com/threefoldtech/zos4/blob/8701df02aa52624bd29f035e7cf69dfae74785c9/pkg/netlight/options/global.go#L13

When forwarding for IPv6 is enables, SLAAC won't accept RA when accept_ra=1 on the interface.
One could set SLAAC to accept RA with accept_ra=2 but that is not a correct solution given that the NS is not a Router.

this needs to be solved for 0-db's to be reachable over public IPv6

[mik-tf]

Any update on this?