qemu.tests.win_virtio_driver_update_test.with_scsi: set cdrom format to ide when using virtio_scsi.

cdrom won't be recognized if virtio_scsi driver is uninstalled,
which will cause install driver failed after uninstall.
Signed-off-by: NCong Li <coli@redhat.com>

qemu/tests/cfg/win_virtio_driver_update_test.cfg

@@ -98,8 +98,10 @@
             target_process = iozone.exe
             run_bgstress = iozone_windows
             drive_format_image1 = ide
+            cd_format_fixed = ide
             q35:
                 drive_format_image1 = ahci
+                cd_format_fixed = ahci
             images += " stg"
             image_name_stg = "images/storage"
             image_size_stg = 4G