libxl: Lists qdisk device in libxl_device_disk_list

As libxl switch to qdisk when blktap isn't available, this patch makes
libxl_device_disk_list also list qdisk device. So
libxl_build_device_model_args_new will be able to add qdisk device to
the command line options of Qemu.

Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
Committed-by: Ian Jackson <ian.jackson@eu.citrix.com>

tools/libxl/libxl.c

@@ -2549,6 +2549,7 @@ libxl_device_disk *libxl_device_disk_list(libxl_ctx *ctx, uint32_t domid, int *n
 
     *num = libxl_append_disk_list_of_type(ctx, domid, "vbd", &disks, &ndisks);
     *num += libxl_append_disk_list_of_type(ctx, domid, "tap", &disks, &ndisks);
+    *num += libxl_append_disk_list_of_type(ctx, domid, "qdisk", &disks, &ndisks);
 
     return disks;
 }