test: Print out actual result when test_succ fails

BUG=none
BRANCH=tot
TEST=make runtests

Change-Id: I419b01d2dd0798bd0a3fe155e41d6aa3d328716a
Signed-off-by: Daisuke Nojiri <dnojiri@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/345586
Reviewed-by: Randall Spangler <rspangler@chromium.org>