Block service commands during installation

While postinst script is configuring freshly installed host, it might
have different environment after a reboot. To prevent misconfiguration
of certain services, don't allow start/stop/restart commands inside
chrooted environment.
Add Salt integration during Debianinstallation

You can enable Salt minion installation on new hosts installed via PXE
and Debian Preseeding (KVM virtual machines, physical hosts). When
enabled, Salt minion will be automatically installed from SaltStack
upstream repository and after a reboot will try to contact 'salt' master
server and register itself.
Merge pull request #12 from drybjed/salt-integration

Salt integration, service start prevention in chroot