only accept etcd based nameserver for /etc/resolv.conf

but still save the local resolvers in /opt/resolv.conf.local in case we want those later
skydns will start with the bootstrap resolver, then 2 skydns-announce services start on the etcd cluster - this way we can drop one out, and our resolv.conf won't get whittled down if we need to restart the skydns-announcements

containers should always /start/ with 3  of the most current nameservers in their resolv.conf, but there's no convenient way to manage the containers' resolv.conf - so containers are expected to have a limited lifespan before needing a restart to refresh nameservers