Append warning message to GRUB menu "ONIE: Install OS"

[david56]

If you go into "ONIE: Install OS" option it will screw up the boot order of the box, and automatically always boot into ONIE instead of the pre-installed NOS. This is a problem and not user friendly, and there should be a warning message in the window, that alerts you that clicking that menu option will reset the boot order. The boot order will not boot into the NOS, until you install a new OS.