Currently, kube-dns always binds to 0.0.0.0 when starting the SkyDNS
server. Sometimes its useful to have it bind to a different address for
testing. So add a new --dns-bind-address flag that can be used to
configure this (default is 0.0.0.0).
For the domain name queries that fail to match any records in the local
kube-dns cache, we check if the queried name matches the federation
pattern. If it does, we send a CNAME response to the federated name.
For more details look at the comments in the code.
