graphite: move carbon package from pip to system's package manager

salt/graphite/files/requirements.txt

@@ -8,5 +8,4 @@ gunicorn
 pytz
 pyparsing
 whisper
-carbon
 graphite-web

salt/graphite/virtualenv.sls

+graphite_carbon:
+  pkg.installed:
+  {% if grains['os_family'] == 'RedHat' %}
+    - name: python-carbon
+  {% else %}
+    - name: graphite-carbon
+  {% endif %}
+
 virtualenv_graphite:
   virtualenv.managed:
     - name: /home/{{ pillar['graphite']['user'] }}/.virtualenvs/graphite