Reland "update_engine_test: Create stateful restore failure marker"

This is a reland of e33bc5f28231704d95969dd7a345ba45e9d2c09a

Original change's description:
> update_engine_test: Create stateful restore failure marker
>
> .. So the lab provisioning can fix stateful in the case that autotest
> restoring stateful wasn't able to. This marker will cause lab
> proviioning to "force" install a stateful partition again.
> Fixing the current stateful mismatch in version with OS.
>
> BUG=b:194760761
> TEST=none
>
> Change-Id: I754e60259ab6b418b2cbd64f6999ea8883818649
> Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/autotest/+/3064843
> Tested-by: Jae Hoon Kim <kimjae@chromium.org>
> Commit-Queue: Jae Hoon Kim <kimjae@chromium.org>
> Reviewed-by: David Haddock <dhaddock@chromium.org>
> Reviewed-by: Xianuo Wang <xianuowang@chromium.org>

Bug: b:194760761
Change-Id: I4da771cae5e02d7c959f9629c33d741786dc8dd5
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/autotest/+/3076128
Tested-by: Jae Hoon Kim <kimjae@chromium.org>
Commit-Queue: Jae Hoon Kim <kimjae@chromium.org>
Reviewed-by: David Haddock <dhaddock@chromium.org>
diff --git a/server/cros/update_engine/update_engine_test.py b/server/cros/update_engine/update_engine_test.py
index 6b1aa23..ca83a02 100644
--- a/server/cros/update_engine/update_engine_test.py
+++ b/server/cros/update_engine/update_engine_test.py
@@ -71,6 +71,8 @@
     # Subtest to use for logging into DUTs in a test.
     _LOGIN_TEST = 'login_LoginSuccess'
 
+    _CORRUPT_STATEFUL_PATH = '/mnt/stateful_partition/.corrupt_stateful'
+
     def initialize(self, host=None, hosts=None):
         """
         Sets default variables for the test.
@@ -726,6 +728,9 @@
 
     def _restore_stateful(self):
         """Restore the stateful partition after a destructive test."""
+        # Fallback to lab provisioning if this function fails to restore.
+        self._run(['touch', self._CORRUPT_STATEFUL_PATH])
+
         # Stage stateful payload.
         ds_url, build = tools.get_devserver_build_from_package_url(
                 self._job_repo_url)