Work on cross-pod sharing.


git-svn-id: https://svn.calendarserver.org/repository/calendarserver@12038 e27351fd-9f3e-4f54-a53b-843176b1656c
normalize group attendees


git-svn-id: https://svn.calendarserver.org/repository/calendarserver@12039 e27351fd-9f3e-4f54-a53b-843176b1656c