Description of problem:
Some API calls that are proxied to candlepin return an incorrect Content-Type header that can cause some clients to fail. Best known case is calling /consumers/{id}/entitlements, with no params. When this call results in no entitlements, the Content-Type returned is 'json', instead of the correct 'application/json'. Candlepin itself returns the correct header value when called directly. 

Version-Release number of selected component (if applicable):
katello-1.1.12-14.el6cf.noarch

How reproducible:
Always

Steps to Reproduce:
1. attempt to consume an entitlement calling /consumers/{id}/entitlements with no arguments.
2.
3.
  
Actual results:
Completely empty return, with a Content-Type header value of 'json'

Expected results:
Empty list ('[]') with Content-Type header value of 'application/json'

Additional info: