Hoist atomicUpdate, deleteKeys up to AbstractAccess

These can be useful in other backends, as they are quite simple
implementations that are built on top of other primitives.

Change-Id: I847ce3b27c18ff4de65d7d5a69cd6690f99ff7bd
Signed-off-by: Shawn O. Pearce <sop@google.com>
2 files changed