Don't ask for password and GECOS while creating vagrant user

live-build/ubuntu-cpc/hooks/042-vagrant.binary

@@ -63,7 +63,9 @@ chroot ${mount_d} apt-get clean
 # Vagrant users expect a "vagrant" user with a "vagrant" username.
 # See https://www.vagrantup.com/docs/boxes/base.html
 # Note: We decided NOT to allow root login with a default password.
-chroot ${mount_d} adduser vagrant
+# --disabled-password and --gecos need to be passed to avoid adduser
+# asking questions when running in an interactive shell
+chroot ${mount_d} adduser vagrant --disabled-password --gecos ""
 echo "vagrant:vagrant" | chroot ${mount_d} chpasswd
 
 # The vagrant user should have passwordless sudo.