[sudo-access] omnidoor security fix

daniel pointed out that the default username "debian" was enabled on the beaglebone black at the front door computer, with the default password AND sudo access. since i think everyone is logging in as root anyway (which has a decent password and most people probably use SSH keys anyway) i disabled the debian account by changing its shell (in /etc/passwd) to /bin/false, and i also set the password to something else anyway. -jake