use mount_ext4.sh to redirect access to recovery partition to /dev/null
This is useful to prevent MIUI Updater App to flash recovery before updating system via recovery.
If you use live-install recovery will still be flashed by install-recovery.sh on  next reboot because custom mount_ext4.sh is missing on the new installation.

Change-Id: Ib8c8ca80b1717b1d6c3e5027c64d2f264be1effb