We don't have to maintain compatibility with both QMP libraries anymore,
so we can just remove the old exception. While we're here, take
advantage of the extra fields present in the VMLaunchFailure exception
that machine.py now raises.
(Note: I'm leaving the logging suppression here unchanged. I had
suggested previously we use filters to scrub the PID out of the logging
information so it could just be diffed as part of the iotest output, but
that meant*always* scrubbing PID from logger output, which defeated the
point of even offering that information in the output to begin with.
Ultimately, I decided it's fine to just suppress the logger temporarily.)
Signed-off-by: John Snow<jsnow@redhat.com>