vboot2: Use calloc() in host lib and unit tests

This is cleaner than malloc() immediately followed by memset().

BUG=chromium:423882
BRANCH=none
TEST=VBOOT2=1 make runtests

Change-Id: Iac32ca54ba18ef6722c6e9c58d521d5337a816b2
Signed-off-by: Randall Spangler <rspangler@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/232770
Reviewed-by: Bill Richardson <wfrichar@chromium.org>
7 files changed