Commit I5b804e09e630d88d551271d9731cc1f65c065259 changed/removed some of the
methods in CommonDbMixin.
As a result the way the plugins register the different extend-dict methods has changed,
and now uses a decorator.
Also those extend-dict callbacks are static methods which do not receive 'self', and
this caused some additional changes.
Change-Id: If99da0ea1e37792bd531ef92b0bbb880d2b05b8a
Depends-on: I5b804e09e630d88d551271d9731cc1f65c065259
8548f110ac