Use bucket var, force a sync

@feanil @jarv 

Sorry for the whitespace changes key change to retire_host.yml at line 41, change to template also important.
I had a PR that was never merged to change this to fail outright if there is an old server that doesn't have send-logs-to-s3 in the tracking.log logrotate file, can you make that change here? see https://github.com/edx/configuration/pull/1505/files