Update with_block to with_viostor

block contain viostor and vioscsi
update with_block to with_viostor s more reasonable
Signed-off-by: NSuqin Huang <shuang@redhat.com>

qemu/tests/cfg/driver_load_stress.cfg

@@ -18,7 +18,7 @@
         - after_bg_test:
             run_bg_flag = "after_bg_test"
     variants:
-        - with_block:
+        - with_viostor:
             driver_name = viostor
             run_bgstress = iozone_windows
             drive_format_image1 = ide