autoinstaller accept a root password, or make a random one

[price]

The autoinstaller is responsible for setting the root password for the new image.

Currently the web interface to the autoinstaller always picks 'password'. This should either be user-supplied, or a random password told to the user.

It may be hard to keep the password out of, e.g., ps output on black-mesa, so the random password may be the better choice.

[price]

Eh. Empty (now the status quo) is fine, as there's no way in but the console until the user installs one.