cros-disks: Add {group,user}/fuse-fusebox

BUG=chromium:1278510
TEST=display-accts.py --show-free; ensure IDs are no longer available

Change-Id: I53e92354b801f847eb5ded808fc37979c83a36c2
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/eclass-overlay/+/3328469
Tested-by: Nigel Tao <nigeltao@chromium.org>
Reviewed-by: Jorge Lucangeli Obes <jorgelo@chromium.org>
Commit-Queue: Nigel Tao <nigeltao@chromium.org>