Don't show cohort information when disabled

TNL-552

@cahrens and I decided that it would be cleaner to have the server return responses as if cohorting had never been enabled, rather than to teach the front end how to ignore the cohort fields.

Reviewers: @cahrens @jimabramson 
This was a strange one. I didn't notice it before, but PyCharm flagged it for me today. It appears to be broken on master too, unless I'm reading it wrong.