Add twext to default modules that are tested.


git-svn-id: https://svn.calendarserver.org/repository/calendarserver@12837 e27351fd-9f3e-4f54-a53b-843176b1656c
Unused module


git-svn-id: https://svn.calendarserver.org/repository/calendarserver@12838 e27351fd-9f3e-4f54-a53b-843176b1656c
Unused module


git-svn-id: https://svn.calendarserver.org/repository/calendarserver@12839 e27351fd-9f3e-4f54-a53b-843176b1656c