Add baham (future ns1) config

This adds it as a fourh DNS server alongside current
ns[012] without disrupting the existing nameservers' configurations.

This is step 1 of a process; it allows us to bring up service
on baham and keep it in sync with ongoing authdns repo updates
without affecting current resolution for the public.

Change-Id: I7c17e0317a54016b23812b929a16db93acda382f