Add use_network_dns_servers, fix dns_server ref

fixes 1128588

Grizzly now allows multiple dns servers when starting dnsmasq, and
can also use the details from the network configuration of the
server to fill in the values.

This change updates the old option and adds a new one.

Change-Id: Ifa7ff675f8dd54cfedd48edfc05e0e3e781a9f7a
Merge "Add use_network_dns_servers, fix dns_server ref"