This commit changes the logic slightly: checking the permissions in the
fuse mount when nobody else besides the current user can access the fuse
mount does not sense. The current user has access to the repo files in
addition to the password, so they can access all data regardless of what
the fuse mount does.
Enabling `--allow-root` allows the root user to access the files in the
fuse mount, for this user no permission checks will be done anyway.
The code now enables `DefaultPermissions` automatically when
`--allow-other` is set, it can be disabled with
`--no-default-permissions` to restore the old behavior.
