val_ta_sentinel* tests: extend tests to cover !AD and +CD
val_ta_sentinel* tests: extend tests to cover !AD and +CD

Sentinel must not require AD/DO bits set in the queries otherwise it
will not work with stubs and web browsers deployed in 2018.

Tests were extended with +CD cases to make sure forwarding
configurations behave as specified by the draft -14.

CZ-NIC/deckard,CZ-NIC/deckard