AUM: ask for additional delay during manual rollback test

Ask to wait a few seconds before to check if undeploy is really
finished. Sometimes the human is too fast to enter commands
so undeploy have no chance to finish before the check.
That is leading to false result of manual test while it works well.

Signed-off-by: Denis Pynkin <denis.pynkin@collabora.com>

test-cases/apertis-update-manager-ota-rollback.yaml

@@ -96,7 +96,7 @@ run:
         Found /extlinux/extlinux-rollback.conf
         Retrieving file: /extlinux/extlinux-rollback.conf
     - "Wait for system boot"
-    - "Check the update has been rolled back and that the initial deployment is still the active deployment"
+    - "Wait a few seconds after the boot to allow ostree to undeploy the deployment. Check the update has been rolled back and that only single deployment exists."
     - $ sudo ostree admin status
     - "Check if the file with blacklisted commit exists"
     - $ cat /var/aum_blacklist.conf

test-cases/apertis-update-manager-rollback.yaml

@@ -86,7 +86,7 @@ run:
         Found /extlinux/extlinux-rollback.conf
         Retrieving file: /extlinux/extlinux-rollback.conf
     - "Wait for system boot"
-    - "Check the update has been rolled back and that the initial deployment is still the active deployment"
+    - "Wait a few seconds after the boot to allow ostree to undeploy the deployment. Check the update has been rolled back and that only single deployment exists."
     - $ sudo ostree admin status
     - "Start the user interface agent"
     - $ sudo updatectl &