debian_installer: Change configuration to use salt
Created by: dcbaker
This removes a number of setup requirements that are now handled by the salt-master/salt-minion, or are updates because they are no longer required.
Basically we've moved as much functionality out of the debian installer as possible and into the salt setup.
A few unrelated changes:
- systemd is the default in debian 8.x, so don't force install it
- drop use of ntpd, use systemd-timesyncd instead. It's already installed and works just as well.