bdb: Enable futility-show to dump key info
bdb: Enable futility-show to dump key info

This change makes futility show command dump information of the keys
found in a BDB.

BUG=chromium:649554
BRANCH=none
TEST=make runtests. run futility show tests/futility/data/bdb.bin

Change-Id: I82bb3956b043adf1febe42941618608865525da2
Signed-off-by: Daisuke Nojiri <fd5f93af191bf7e8f73ea71cc3c0f66b41b1dd49@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/399059
Reviewed-by: Randall Spangler <62698fdbb84d1779579ee80c3f39fac22017e5bc@chromium.org>

coreboot/vboot,coreboot/vboot,coreboot/vboot,coreboot/vboot,coreboot/vboot