Change CONFLICT to SERVICE_UNAVAILABLE for memcache lock timeouts.


git-svn-id: https://svn.calendarserver.org/repository/calendarserver@11954 e27351fd-9f3e-4f54-a53b-843176b1656c
Merge in r11892 through r11948


git-svn-id: https://svn.calendarserver.org/repository/calendarserver@11955 e27351fd-9f3e-4f54-a53b-843176b1656c
add group changes back to txdav.common.datastore.sql, converting uuid -> str when needed


git-svn-id: https://svn.calendarserver.org/repository/calendarserver@11956 e27351fd-9f3e-4f54-a53b-843176b1656c
fix GroupAttendeeReconciliationWork setting of MEMBER param on attendee property


git-svn-id: https://svn.calendarserver.org/repository/calendarserver@11957 e27351fd-9f3e-4f54-a53b-843176b1656c
Add (empty) index test classes


git-svn-id: https://svn.calendarserver.org/repository/calendarserver@11958 e27351fd-9f3e-4f54-a53b-843176b1656c