block: Use child_of_bds in remaining places

Replace child_file by child_of_bds in all remaining places (excluding
tests).

Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20200513110544.176672-28-mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
diff --git a/block.c b/block.c
index d138a3c..fb94adc 100644
--- a/block.c
+++ b/block.c
@@ -3406,7 +3406,8 @@
         BlockDriverState *file_bs;
 
         file_bs = bdrv_open_child_bs(filename, options, "file", bs,
-                                     &child_file, 0, true, &local_err);
+                                     &child_of_bds, BDRV_CHILD_IMAGE,
+                                     true, &local_err);
         if (local_err) {
             goto fail;
         }