kboot: Make console raw when we start

Put the console into raw mode on startup. This allows the menus to work
as expected. Boot is now interruptable.

Note: Likely should restore the terminal settings on most exists. It's
not clear the best way to do this, and most shells have an auto stty
sane anyway, so note it for future improvement.

Sponsored by: Netflix

(cherry picked from commit 9579540144880e0a612ec2fdfc66de46c08d28d6)