Use --delay-updates on rsync upload to minimize time of inconsistency in the repo

Use --delay-updates on rsync upload to minimize time of inconsistency in the repo

During the rsync operation, package lists could go out of sync with the
.ipk files, or a mirror might be pulling an incomplete list of files.
To reduce the chance of this happening, let rsync put all updated files
into place at the end of the transfer

Signed-off-by: Felix Fietkau <[email protected]>