Cleanup unused DB APIs, part I

Cleanup unused DB APIs, part I

There are unused DB APIs, some of them were leftovers of other features
removal, some are purely added without being used.  This change removes
these unused DB APIs.

Note that there are some DB APIs only used by unit tests, in other words
they are used in unit tests where they are not the unit of code being
tested. Those will be cleaned up in follow-up patch(es).

Change-Id: I456e64445dc8a258fdcc3c1b309f59f8adcc23e3