qemu.tests.pci_devices: Add virtio_disk testing devices

This patch adds the possibility to use virtio_disks for testing.

Signed-off-by: Lukáš Doktor <ldoktor@redhat.com>
qemu.tests.pci_devices: Add support for uhci test device

Make it possible to use ich9-usb-uhci controller for pci_devices testing

Signed-off-by: Lukáš Doktor <ldoktor@redhat.com>
virttest.qemu_devices: Fix the bug with overwritten bus for virtio disk

The bus property of virtio disks is set by pci_bus and is set during
device insertion via parent_bus.

Signed-off-by: Lukáš Doktor <ldoktor@redhat.com>
qemu.tests.pci_devices: Major config update

Original setups were only for developing the test and some of them
were invalid (impossible for real hw and thus unsupported by kernel).
These setups were checked with pci device developer and they should be
working properly.
virttest.qemu_devices: Split qemu_devices into separate submodules

qemu_devices is becoming way too long. This patch splits it into
logical modules: qdevices, qbuses and qcontainer.

I perserved the qemu_devices_unittest in the same form for now,
but it can be split in the future. It already is sepparated into
three classes.

Signed-off-by: Lukáš Doktor <ldoktor@redhat.com>
qemu.tests.multi_disk_random_hotplug: Update to latest qemu_devices

qemu_devices doesn't support force nor unplug for some time,
this patch fixes this test.

Signed-off-by: Lukáš Doktor <ldoktor@redhat.com>
qemu.tests.multi_disk_random_hotplug: Fix pseries only setting

spapr_vscsi is supported only on pseries.

Signed-off-by: Lukáš Doktor <ldoktor@redhat.com>