bisect-kit: explain why reboot failed

BUG=None
TEST=None

Change-Id: Ib74f4e643f29ed5d93bbb636810c1fd50aac49ae
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/bisect-kit/+/3530473
Tested-by: Kuang-che Wu <kcwu@chromium.org>
Auto-Submit: Kuang-che Wu <kcwu@chromium.org>
Reviewed-by: Zheng-Jie Chang <zjchang@chromium.org>
Commit-Queue: Zheng-Jie Chang <zjchang@chromium.org>
1 file changed