Improve coverage of cgptlib.c

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

Change-Id: I5719c6b8aa1a23fc65bf38d7096320479152f0ca
Signed-off-by: Randall Spangler <rspangler@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/41955
Reviewed-by: Bill Richardson <wfrichar@chromium.org>
3 files changed