host.adduser and contrib.unison fails to create valid user

[Stuart Bishop]

contrib.unison calls host.adduser to create an account, without specifying a password. This would be fantastic, since we don't want a password since we are setting up ssh access, except it fails. host.adduser detects the lack of password, and calls useradd with the --system option. This option is explicitly documented as not creating the home directory, so subsequent attempts to setup ~/.ssh fail.

Fix is to generate a random password, or fix host.adduser to properly create passwordless accounts.