Parse the -M (or -machine) command line option before starting
processing in earnest and have a fallback ready in case it's not
present, so that while parsing other options we can rely on
def->os.machine being initialized.
Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1379218
Signed-off-by: Andrea Bolognani <abologna@redhat.com>
Reviewed-by: Daniel P. Berrange <berrange@redhat.com>
