[fido] Improve Robustness of U2fBleDiscovery and U2fRequest

This change improves the robustness of U2fBleDiscovery by checking for
adapter presence in the destructor and modifies U2fRequest to respect
the success argument for DiscoveryStarted.

Bug: 809721
Change-Id: I889514a0a02948913f7475ca5b142feeebe5fa25
Reviewed-on: https://chromium-review.googlesource.com/915344
Commit-Queue: Jan Wilken Dörrie <jdoerrie@chromium.org>
Reviewed-by: Balazs Engedy <engedy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#536363}
6 files changed