Remove AmazonProvidedDNS from DHCP option set

[CaptainCodeman]

Only the NAT instance should reference the AmazonProvidedDNS, all other instances should use the NAT instance for DNS (which will forward non-internal DNS requests to the AmazonProvidedDNS).

Linux appears to use nameservers in order whereas Windows would suddenly switch to using the different name server which could returned a previously used DNS address and confuse running clients even if the client connected to the server via IP address (how the C# driver discovers the replica-set so ends up connecting via hostname).

Need to make sure that NAT instance can resolve names during init for it to install updates, packages etc...