Fix format string spec - need" :d" not "!d".


git-svn-id: https://svn.calendarserver.org/repository/calendarserver@12714 e27351fd-9f3e-4f54-a53b-843176b1656c
Don't fail if new attachment hashed directory already exists.


git-svn-id: https://svn.calendarserver.org/repository/calendarserver@12715 e27351fd-9f3e-4f54-a53b-843176b1656c