Before this change, if --fast-list was in use while doing a sync or
copy with --create-empty-src-dirs and --exclude excluded all the files
from the directory (but not the directory), then the directory would
not be created.
This is also visible with `rclone tree` which uses the same tree
building approach as `rclone sync --fast-list` where the directories
would go missing from the tree view.
This was caused by not adding the parents of excluded files to the
directory tree.
See: https://forum.rclone.org/t/create-empty-src-dirs-issue-with-b2/30856
da404dc0f2