image_signing: use per-board release file blacklist

This patch changes ensure_no_nonrelease_files.sh to use per-board
release file blacklist instead of the default one.  It also uses this
opportunity to make ensure_no_nonrelease_files.sh consistently
formatted.

BRANCH=none
TEST=Ran ./security_test_image on a lakitu image and --vboot_hash
pointing to this commit, and verified ensure_no_nonrelease_files.sh passes.
BUG=brillo:823

Change-Id: I2cff56192a5ff0b917faba7549e7adafb4757a47
Reviewed-on: https://chromium-review.googlesource.com/267335
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Commit-Queue: Amey Deshpande <ameyd@google.com>
Tested-by: Amey Deshpande <ameyd@google.com>
3 files changed