add cloud-init/confd.yaml with confd unit; relink user-data to confd.yaml
move skydns dns_addr from conf to command line option to avoid conflicts on multi-nodes cluster
add confd confdir under registry-conf
modify registry units for using confd to generate nginx proxy site conf file
use  for docker daemon because the coreos env may not be available yet.
increase the TimeoutStartSec value for slow home network