revert_eve_image_update: introduce wait for eden

seems eden might be slow
(https://github.com/lf-edge/eve/actions/runs/26049351775/job/76699979389 )

Signed-off-by: Christoph Ostarek <christoph@zededa.com>

Author: christoph-zededa

tests/update_eve_image/testdata/revert_eve_image_update.txt

@@ -49,12 +49,12 @@ cmp stdout ver
 # controller-side state.
 eden -t 1m controller edge-node eveimage-remove file://{{EdenConfigPath "eve.dist"}}/rootfs-{{ $short_version }}.squashfs -m adam:// --os-version={{ $short_version }}
 
+exec sleep 10
+
 # Verify the controller config no longer references the removed image
 eden controller edge-node get-config
 ! stdout '{{ $short_version }}'
 
-exec sleep 10
-
 # Test's config file
 -- eden-config.yml --
 test: