tests/acceptance/virtio_check_params: List machine being tested

tests/acceptance/virtio_check_params: List machine being tested

Add logging for easier debugging of failures:

  $ avocado --show=machine run tests/acceptance/virtio_check_params.py
   (1/1) tests/acceptance/virtio_check_params.py:VirtioMaxSegSettingsCheck.test_machine_types:
  machine: {'name': 'pc-i440fx-2.12', 'seg_max_adjust': 'false', 'device': 'virtio-scsi-pci'}
  machine: {'name': 'pc-i440fx-2.0', 'seg_max_adjust': 'false', 'device': 'virtio-scsi-pci'}
  machine: {'name': 'pc-q35-4.2', 'seg_max_adjust': 'false', 'device': 'virtio-scsi-pci'}
  machine: {'name': 'pc-i440fx-2.5', 'seg_max_adjust': 'false', 'device': 'virtio-scsi-pci'}
  machine: {'name': 'pc-i440fx-4.2', 'seg_max_adjust': 'false', 'device': 'virtio-scsi-pci'}
  ...

Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Message-Id: <20200129212345.20547-19-philmd@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>