In c5ac96e9e7 we made --files-from only read the objects specified and
don't scan directories.
This caused problems with Google drive (very very slow) and B2
(excessive API consumption) so it was decided to make the old
behaviour (traversing the directories) the default with --files-from
and use the existing --no-traverse flag (which has exactly the right
semantics) to enable the new non scanning behaviour.
See: https://forum.rclone.org/t/using-files-from-with-drive-hammers-the-api/8726Fixes#3102Fixes#3095