vm: output the error when VM failed to start
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 <52dc720c411f8e2156e608c1a8b894a917489667@chromium.org>
Commit-Queue: Yu-Ju Hong <52dc720c411f8e2156e608c1a8b894a917489667@chromium.org>
Tested-by: Yu-Ju Hong <52dc720c411f8e2156e608c1a8b894a917489667@chromium.org>

bpsinc-native/src_third_party_chromite,chadversary/chromiumos.chromite,chadversary/chromiumos.chromite,bpsinc-native/src_third_party_chromite,bpsinc-native/src_third_party_chromite