Removed invalid content type that was reintroduced, breaking group requests

This broke between 2.1.1 and 2.1.2 with commit bc39b176754b762f0af8c68462a33c62e108d1e4

I've also made an addition to the crowd spec that responds in the same way Crowd will respond to this content type header, and made corrections to the 'should have good data' steps.