Two methods were recently added to the testcontrol.Server type:
AddDNSRecords and SetGlobalAppCaps. These two methods should trigger
netmap updates for all nodes connected to the Server instance, the way
that other state-change methods do (see SetNodeCapMap, for example).
This will also allow us to get rid of Server.ForceNetmapUpdate, which
was a band-aid fix to force the netmap updates which should have been
triggered by the aforementioned methods.
Fixestailscale/corp#37102
Signed-off-by: Harry Harpham <harry@tailscale.com>