Partition server start/stop in upgrade process

Users would like to be physically present when their servers are being started or stopped to ensure they can fix anything that goes wrong promptly.  However sitting through lengthy data downloads and uploads is not so fun.  This allows them to only be present when servers are starting/stopping.

More context: https://chef.leankit.com/Boards/View/87539983/129913878
CI: http://wilson.ci.opscode.us/job/chef-server-12-trigger-ad_hoc/103/
What's the point here of setting this to default? I figure the intent is not to have it be empty if the code underneath ever changes, but I actually think null might be better. As the code is currently written this will either never be used or else be overwritten. If the code does happen to change and this does somehow get passed through as "default", it eventually ends up as the directory used. If the user happens to have a directory named default, then that one will be used. It'll likely be as strange an error as it failing with a null value.