ENH: manage puppetd startup on debianesque systems

This PR manages the `/etc/default/puppet` config file in a more sensible way: On debianesque systems, puppet will set `START=yes` only if `runmode==server` and `START=no` otherwise. Current behavior will leave the config file untouched if `runmode!=server`. This is problematic in cases where `START=yes` is set by a provitioning process before the node gets managed by puppet, and you have `runmode=cron` in your config.

The new behaviour will disable puppetd in these cases.

Additionally, a new config parameter `client_daemon_opts` is introduced which sets the `DAEMON_OPTS` parameter in the config file.