Fix attachment content-types test.
Fix attachment content-types test.

git-svn-id: f80e50af2c1eba29925bef1c136b651f2efe9314@5904 e27351fd-9f3e-4f54-a53b-843176b1656c

red-hood/calendarserver,red-hood/calendarserver,red-hood/calendarserver,red-hood/calendarserver,red-hood/calendarserver,red-hood/calendarserver