Preserve patched_at across the post-restart re-mount

create_task.py verify decides "loaded" by comparing middlewared's start time
against hook_status.json's patched_at. The post-restart re-mount restores the
same patch the boot pass already applied, but it runs after the restart — so
letting apply.sh re-stamp made patched_at newer than the process that had
correctly imported the patch, and verify reported FAIL while everything was
working. That would have fired on every boot where docker's nvidia sysext
merge detaches the overlay.

Found on hardware while exercising the candidate: a new lying status
introduced by the fix for a lying status. The snapshot lives in /run, not the
repo — a leftover file there would leave the tree dirty, which update.sh
refuses to run over.

tests/test_wait_restart.py

@@ -172,3 +172,28 @@ def test_mount_retries_on_a_private_workdir():
     body = src[start:end]
     assert body.count("mount -t overlay") == 2, "expected a retry mount"
     assert 'work="/run/truecloud-${tag}-work.$$"' in body
+
+
+def test_post_restart_remount_preserves_the_patched_at_stamp():
+    """create_task.py verify compares middlewared's start time to patched_at.
+
+    The post-restart re-mount restores the same patch the boot pass applied, so
+    letting apply.sh re-stamp would make patched_at newer than the process that
+    correctly imported it -- verify would then report FAIL forever on every boot
+    where docker's sysext merge detaches the overlay.
+    """
+    src = wait_restart_source()
+    tail = src[src.index("systemctl try-restart middlewared"):]
+    assert "hook_status.json" in tail
+    save = tail.index("/run/truecloud-hook_status.pre")
+    reapply = tail.index("TRUECLOUD_REAPPLY=1")
+    restore = tail.rindex("hook_status.json")
+    assert save < reapply < restore, "snapshot must bracket the re-apply"
+
+
+def test_status_snapshot_is_not_written_into_the_repo():
+    """A leftover file in the repo dir leaves the tree dirty, and update.sh
+    refuses to run over a dirty tree -- that once made the patch un-updatable."""
+    src = wait_restart_source()
+    assert "/run/truecloud-hook_status.pre" in src
+    assert '"$PATCH_DIR/hook_status.json.pre' not in src