init: Add UMA FS error stats

Move send-kernel-error code from .conf file.
Add unit tests.
Report to UMA when stateful/encrypted stateful have some errors.

BUG=chromium:760007
CQ-DEPEND=CL:682355
TEST=Unit test, check on gnawty

Change-Id: Ibbc0c25a5d4baa06624cd638e63dc289a37c48c4
Signed-off-by: Gwendal Grignou <gwendal@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/682596
Reviewed-by: Mike Frysinger <vapier@chromium.org>
8 files changed