autotest/virt-test — pull request #1073 by yumingfei (2013-11-15 07:45:12+00:00)
Title: virttest.libvirt_vm: Raise stderr of virsh.start after starting failed.

Double "VB failed to start." will be printed out here.
It's not easy to know what's the real reason, so replacing one with result.stderr.

Signed-off-by: Yu Mingfei