show proper node when scheduling instance reboots
We were wrongly implying where the instance was located.
Before:
11:45:05 scheduled shutdown with 10 minute delay on fsn-node-01.torproject.org instances: check-01.torproject.org
After:
11:45:05 scheduled shutdown with 10 minute delay on fsn-node-05.torproject.org instances: check-01.torproject.org
This is not pretty: we're not really using the node_con other than the
notification and it can be inaccurate if we actually call
stop_instances on instances that spread among multiple nodes, but the
typical reboot
case is fine.