puppet_command: set hostname manually, not via puppet.

i am really tired of all the errors caused by the way we apply puppet (first setup.pp, then init.pp). we don't seem to be capable of creating non-flapping manifests (where a change in init.pp is undone by the next call to setup.pp). 

this commit makes it so that the hostname is properly set in puppet_command

there may have been some other ill conceived reason for setup.pp, but i don't remember it.