Merge pull request #4388 from qingwangrh/4590_fix_boot_and_windows_dd

disk_extension:fix boot error and change to dd

Author: XueqiangWei

qemu/tests/cfg/disk_extension.cfg

@@ -18,6 +18,7 @@
     loop_device_img_tag = "stg1"
     images += " ${loop_device_img_tag}"
     boot_drive_stg0 = no
+    image_boot = yes
     image_raw_device_stg0 = yes
     image_name_stg0 = ${tmpfs_folder}/stg0.raw
     image_size_stg0 = ${begin_size}
@@ -33,7 +34,7 @@
     Linux:
         guest_cmd = "dd if=/dev/urandom of=%s oflag=direct bs=${max_size}"
     Windows:
-        guest_cmd = "WIN_UTILS:\coreutils\DummyCMD.exe %s ${max_size_in_bytes} 1"
+        guest_cmd = "WIN_UTILS:\dd.exe if=/dev/random of=%s bs=1M count=500"
         cd_format_cd1 = ide
     virtio_blk:
         driver_name = viostor