SYS READ-ONLY is not restored by poweroff script

[DrUm78]

A very important issue occurs when powering off the system after enabling "SYS READ-WRITE" with Commander. It seems that SYS READ-ONLY is not restored when turning off the system with /sbin/poweroff (as discussed with Vincent on Discord).

Steps to reproduce:

1. Open Commander under GMenu2X
2. Press Menu button and choose "SYS READ-WRITE"
3. Turn OFF the system with Menu button (keep it pressed)
4. Turn the system ON again and try to launch any OPK
5. Notice that it sends you back to GMenu2X
6. Open the GMenu2X output log and read "Unable to mount OPK: No such file or directory"

Workaround:
To avoid this bug, you have to restore "SYS READ-ONLY" in Commander before powering off the system.
Once the bug occurs, the only way to fix it is to enter recovery mode (Fn+START on boot), mount the usb device (as that's not possible anymore from GMenu2X), drag and drop the firmware and update it again.

[DrUm78]

Fixed and verified (tested with old Commander that did not have the restored read-only fix) in firmware 2.1.0.