test_twisted: rewrite with inlineCallbacks
test_twisted: rewrite with inlineCallbacks

Also, we now disable confirmation to exercise a verifier mismatch. An
upcoming implementation change can probably detect the mismatch too
early otherwise, and throw WrongPasswordError before the test can
compare the verifiers.

warner/magic-wormhole,warner/magic-wormhole,warner/magic-wormhole,warner/magic-wormhole