dual-image: Sync files before sync-manager starts

The sync-manager only sync files when it's changed/deleted, but does not
sync when it's untouched.
If the service starts and there is no change, the files will not be
synced.

Mount the rwfs-alt and add a script to sync the files before the
sync-manager starts, so that they are always synced when the
sync-manager is running.

Tested: Verify the files are synced before the sync-manager starts.

Signed-off-by: Lei YU <yulei.sh@bytedance.com>
Change-Id: I5613738b7b490201c556a175425b48aebae1505b
3 files changed