Add node discovery
Add a new node and new node ack for UDP discovery.
Fix discovery test
fix typo
We don't need to get the fqdn again
Fix discovery
Add fqdn to circus-stats plugin.
send the nodes, not data
Remove bad logger import
conver sets to list for json encoding
fqdn → fqdn prefix
update the discovery tests
Merge remote-tracking branch 'origin/node-discovery' into add-fqdn-stats
Revert "start to refactor the controller module"

This reverts commit 7371d0c41ae23006b6414c96c6e0fb9e1204cc9f.
Merge remote-tracking branch 'origin/add-fqdn-stats' into async-tornado
We don't need this endpoint anymore.