Before the fix we were only de-duping the ListR batches.
Afterwards we dedupe everything.
This will have the consequence that rclone uses more memory as it will
build a map of all the directory names, not just the names in a given
directory.
This dramatically increases the speed (7x in my tests) of the de-dupe
as google drive supports ListR directly and dedupe did not work with
`--fast-list`.
Fixes#2902
