[CHEF-4435] EC11 + OSS breaks /data endpoint for Chef 10

Might want to produce an include from this change and then include it in breaking changes for both Chef 11.6.x as well as EC11 + OSS . That way, anyone coming in from anywhere can see that something weird has happened with the /data endpoint. CHEF-4435 goes into detail about a Chef 10 client's behavior with the new servers.  Chef 11.6.x clients handle are fixed to handle the modified endpoint behavior properly.