Teach QEMUMonitorProtocol to accept an exisiting socket.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-id: 20230111080101.969151-3-marcandre.lureau@redhat.com
Signed-off-by: John Snow <jsnow@redhat.com>