Support trivial delete by key

Currently the SQL backend assumes the full object instance
during the translation routines, so implement deleteKeys
by loading the objects, and then deleting what we found.

Change-Id: Ie1a112551135ad9e2f82b167f5dfefb78e8c07c6
Signed-off-by: Shawn O. Pearce <sop@google.com>
2 files changed