Ensure initialisation of AuthenticatorSupportedOptions' fields

Add a default member initialization for client_pin_availability_
to prevent use of un-initialized memory (found by MSan).

Bug: 859816
Change-Id: I5ab81ee60a6aed657f44a8bee7d094dc14f030b9
Reviewed-on: https://chromium-review.googlesource.com/1123828Reviewed-by: Jun Choi <hongjunchoi@chromium.org>
Commit-Queue: Jun Choi <hongjunchoi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#572254}

device/fido/authenticator_supported_options.h

@@ -72,7 +72,8 @@ class COMPONENT_EXPORT(DEVICE_FIDO) AuthenticatorSupportedOptions {
   bool user_presence_required_ = true;
   // Represents whether client pin in set and stored in device. Set as null
   // optional if client pin capability is not supported by the authenticator.
-  ClientPinAvailability client_pin_availability_;
+  ClientPinAvailability client_pin_availability_ =
+      ClientPinAvailability::kNotSupported;
 
   DISALLOW_COPY_AND_ASSIGN(AuthenticatorSupportedOptions);
 };