removeFromServerNetwork and CleanUp hardcoded useNewDNSRoute=false
when building the router pair for RemoveNatRule. This meant the
destination was a Prefix (0.0.0.0/0) instead of a DomainSet, so the
IsSet() branch in RemoveNatRule that removes the v6 duplicate never
triggered. The v6 NAT rule leaked until the next full Reset.
Store useNewDNSRoute on the Router from UpdateRoutes and use it
consistently in removeFromServerNetwork and CleanUp, making add
and remove symmetric.
Viktor Liu