Improve Datastore Not Implemented exceptions

Added exception for not implemented exceptions
that indicates the operation name.
Added missing un-implemented methods to redis.
Change handling of remote errors from guest agent
api to only pass along the root exception message
rather than the full traceback

Change-Id: I0d4fdc5340bfb40370595636cc57cc5c87889507
Closes-Bug: #1276860
Merge "Improve Datastore Not Implemented exceptions"