vm: output the error when VM failed to start

BUG=None
TEST=None

Change-Id: I0c877d0138bebe3ac925238c5f020db923db648f
Reviewed-on: https://chromium-review.googlesource.com/187916
Reviewed-by: Yu-Ju Hong <yjhong@chromium.org>
Commit-Queue: Yu-Ju Hong <yjhong@chromium.org>
Tested-by: Yu-Ju Hong <yjhong@chromium.org>
(cherry picked from commit d269cff9f28451dc80c87673f3ae0ec3bc7c5739)
Reviewed-on: https://chromium-review.googlesource.com/188168
1 file changed