Move all bot health images into an images/ directory

TBR=eyaich@chromium.org

Bug: 842232
Change-Id: I01d6db483807f9e7840434f586e608b8d92a490a
Reviewed-on: https://chromium-review.googlesource.com/1062285
Reviewed-by: Charlie Andrews <charliea@chromium.org>
Commit-Queue: Charlie Andrews <charliea@chromium.org>
Cr-Commit-Position: refs/heads/master@{#559191}
17 files changed