fido/win: fix two bugs in attestation response handling

1) Pass the converted |dwTransportUsed| value into the response.
2) Require the attestation statement be a map, not just any CBOR value.

Also add unit tests.

Change-Id: Ifcf2c4936b08a45eed0be648be6307d71b48a9f1
Reviewed-on: https://chromium-review.googlesource.com/c/1429620
Commit-Queue: Adam Langley <agl@chromium.org>
Reviewed-by: Adam Langley <agl@chromium.org>
Cr-Commit-Position: refs/heads/master@{#625243}
3 files changed