build_image: stop inserting container key

The only code that called this was in crosh, and that code is gone.

BUG=chromium:976916
TEST=cq passes

Cq-Depend: chromium:1666234
Change-Id: I940161682d36b9f29d7217a7c5d96d350b104e93
Reviewed-on: https://chromium-review.googlesource.com/1666480
Tested-by: Mike Frysinger <vapier@chromium.org>
Commit-Ready: Mike Frysinger <vapier@chromium.org>
Legacy-Commit-Queue: Commit Bot <commit-bot@chromium.org>
Reviewed-by: LaMont Jones <lamontjones@chromium.org>
1 file changed