Fix issue with find_mapping existing on bad usb device.

Fixed some failing tests

BUG=b:411473239
TEST=pylint in labstation/usb_hubs

Change-Id: Ie36e314e122b4cf619cb301fa84cb8cecf5b93e6
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/labstation/+/6507281
Reviewed-by: Garry Wang <[email protected]>
Auto-Submit: Keith Haddow <[email protected]>
Tested-by: Keith Haddow <[email protected]>
Commit-Queue: Garry Wang <[email protected]>
5 files changed