Added a metric for tracking non-zero TPM dictionary-attack counters.

BUG=chromium:341358
TEST=manual

Change-Id: I99d3e4279c6d9185b9b515259d4fe511e0d79874
Reviewed-on: https://chromium-review.googlesource.com/185493


Reviewed-by: Luigi Semenzato <semenzato@chromium.org>
Commit-Queue: Darren Krahn <dkrahn@chromium.org>
Tested-by: Darren Krahn <dkrahn@chromium.org>