Smart Lock: Remove authentication caching mechanism.

The EasyUnlock V1 setup flow is being removed, so this caching mechanism
is not necessary at the moment and helps break up the removal change.

R=hansberry@chromium.org

Bug: 899324
Test: none
Change-Id: I7a15a78d95edf5585636dc398f708fa12a7e0bc7
Reviewed-on: https://chromium-review.googlesource.com/c/1306348
Commit-Queue: James Hawkins <jhawkins@chromium.org>
Reviewed-by: Ryan Hansberry <hansberry@chromium.org>
Reviewed-by: Alexander Alekseev <alemate@chromium.org>
Cr-Commit-Position: refs/heads/master@{#604272}
9 files changed