OC-7481: chef-server-core: less the webui + unicorn
OC-7481: disable the webui by default in chef-server-core

Since the webui is not installed, we can't configure it.

Down the road we'll have to revist how we do this when we no longer ship the webui with the API server by default.
Clean up crufty upgrade instructions

Apparently OSC doesn't have a chef-server-ctl upgrade and we don't use /etc/opscode