Use class param for user home

Set the users home to $::grpahite::root_dir
gunicorn_bin logic in class not template

Moving the logic out of the template and putting it in the class file,
should hopefully make it clearer about what is actually happening.
Fix initdb command

Incorrect path was being used for manage.py when pip is used. Also fully
qualify path to Python when Pip is not being used.
Remove ownership fo config files

The graphite user will no longer own the the configuration files but can
still read, allowing the services to start.