Add more scenerios for viostor/vioscsi test

Add scenerios for virstor/vioscsi test
e.g run iozone in system disk/data disk before/during/after sub tests (shutdown, reboot)

qemu/tests/cfg/virtio_storage_in_use.cfg

+- virtio_storage_in_use:
+    type = driver_in_use
+    start_vm = yes
+    kill_vm_on_error = yes
+    check_guest_bsod = yes
+    login_timeout = 240
+    suppress_exception = no
+    run_bgstress = iozone_windows
+    target_process = iozone.exe
+    cdrom_cd1 = isos/windows/winutils.iso
+    only Windows
+    variants:
+        - before_bg_test:
+            run_bg_flag = "before_bg_test"
+        - during_bg_test:
+            suppress_exception = yes
+            run_bg_flag = "during_bg_test"
+        - after_bg_test:
+            run_bg_flag = "after_bg_test"
+    variants:
+        - with_stop_continue:
+            suppress_exception = no
+            sub_test = stop_continue
+        - with_shutdown:
+            sub_test = shutdown
+            shutdown_method = shell
+        - with_reboot:
+            sub_test = boot
+            reboot_count = 1
+            reboot_method = shell
+        - with_system_reset:
+            sub_test = boot
+            reboot_method = system_reset
+            sleep_before_reset = 20
+    variants:
+        - system_disk:
+            disk_letter = C
+        - data_disk:
+            disk_letter = I
+            disk_index = 1
+            format_disk = yes
+            images += " stg"
+            image_name_stg = "images/storage"
+            image_size_stg = 4G
+            force_create_image_stg = yes
+            remove_image_stg = yes
+    variants:
+        - with_block:
+            driver_name = viostor
+            drive_format = virtio
+            iozone_cmd = "WIN_UTILS:\Iozone\iozone.exe -azR -r 64k -n 1G -g 2G -M -i 0 -i 1 -b iozone.xls -f ${disk_letter}:\testfile"
+            iozone_timeout = 7200
+            wait_bg_time = 180
+        - with_vioscsi:
+            driver_name = vioscsi
+            drive_format = scsi-hd
+            iozone_cmd = "WIN_UTILS:\Iozone\iozone.exe -azR -r 64k -n 1G -g 2G -M -i 0 -i 1 -b iozone.xls -f ${disk_letter}:\testfile"
+            iozone_timeout = 7200
+            wait_bg_time = 180