allow config/sdcardfs directory to be seen for ARC++

Normally, the whole configfs is mounted on /config and /config will be
word readable:

sailfish:/ $ ls -ld /config/*
drwxrwx--- 258 system package_info 0 2018-05-08 16:08 /config/sdcardfs
sailfish:/ $ ls -ld /config/
drwxr-xr-x 3 root root 0 1969-12-31 16:00 /config/

On ARC++, we only mount-bind config/sdcardfs, so it is important that
/config is set properly.

It is actually 0500, so system could not see /config/sdcardfs, even if
/config/sdcardfs is set properly:
Although root can, as system uid, we can not reach /config/sdcardfs:
:/ $ ls -ld /config
dr-x------ 3 root root 31 2018-05-02 21:56 /config
:/ $ ls -ld /config/sdcardfs
ls: /config/sdcardfs: Permission denied

With this change, system (and systemservice) is able to reach
/config/sdcardfs:
:/ $ ls -ld /config
dr-xr-xr-x 3 root root 31 2018-05-02 21:56 /config
:/ $ ls -ld /config/sdcardfs
drwxrwx--- 109 system package_info 0 2018-05-08 15:29 /config/sdcardfs

Bug: 63876697
Test: After change, package service is able to create the bindings in
/config/sdcardfs.

Change-Id: I7e9b99d7af2ad001fbb1b95bee35d494e861be78
Signed-off-by: Gwendal Grignou <gwendal@google.com>
1 file changed