Improve coverage of vbnvstorage test

BUG=chromium-os:38139
BRANCH=none
TEST=make runtests

Change-Id: I93aabedb99fdeba01954a4b59e3e089b4087380c
Signed-off-by: Randall Spangler <rspangler@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/41850
Reviewed-by: Bill Richardson <wfrichar@chromium.org>
2 files changed