qemu.tests.cfg: Update sr_iov_file_transfer.cfg

Signed-off-by: Feng Yang <fyang@redhat.com>
tests.shutdown: Support shutdown guest for multi times.

Signed-off-by: Feng Yang <fyang@redhat.com>
qemu.tests.multi_vms_file_transfer: Type fix, correct log filename.

Signed-off-by: Feng Yang <fyang@redhat.com>
qemu.tests: Rename sr_iov_hotunplug.py -> qemu/tests/pci_hotunplug.py

sr_iov_hotunplug.py is not only used by sr-iov test case. So rename it
as pci_hotunplug.py

Signed-off-by: Feng Yang <fyang@redhat.com>
qemu.tests.cfg: Add device_assignment new test case

This test cover some device assignment feature test case

Signed-off-by: Feng Yang <fyang@redhat.com>