Previous to this change rclone cached the looked up root_folder_id in
the root_folder_id config variable.
This has caused a lot of confusion and a few attempts at workarounds
and ultimately was a mistake.
This reverts rclone attempting to cache anything in root_folder_id and
returns that variable to be entirely user modified.
It gives a little hint in the debug that rclone could be sped up
slightly by setting it, but it is up to the user to think about
whether that would be OK or not.
Google drive root '': root_folder_id = "XXX" - save this in the config to speed up startup
It does not change root_folder_id itself, leaving this to the user.
See: https://forum.rclone.org/t/rclone-gdrive-no-longer-returning-anything/17215
f50ab981f7