It is already the case that a DELETE of a deleted object results in a
404, and GET/HEAD/POSTs to both expired and deleted objects result in
404s. However, a DELETE of an expired object resulted in a 202. This
change makes it consistent with the other verbs.
Fixes bug 1076245.
Change-Id: I793e62d72461a4fb9fb3404e10658ddcc4c3a7a6