python: QEMUMachine: enable qmp accept timeout by default

python: QEMUMachine: enable qmp accept timeout by default

I've spent much time trying to debug hanging pipeline in gitlab. I
started from and idea that I have problem in code in my series (which
has some timeouts). Finally I found that the problem is that I've used
QEMUMachine class directly to avoid qtest, and didn't add necessary
arguments. Qemu fails and we wait for qmp accept endlessly. In gitlab
it's just stopped by timeout (one hour) with no sign of what's going
wrong.

With timeout enabled, gitlab don't wait for an hour and prints all
needed information.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Reviewed-by: John Snow <jsnow@redhat.com>
Message-Id: <20220624195252.175249-1-vsementsov@yandex-team.ru>
[Fixed typing. --js]
Signed-off-by: John Snow <jsnow@redhat.com>