Implement support for query only clients in Rapi

This implements the same query=True|False functionality as in
GetClient for cli.py, however since the RAPI code is much more
unit-tested (and the unit-test clients are mocked, for the most part,
without support for addresses) we have to do many adaptations in the
tests.

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Agata Murawska <agatamurawska@google.com>