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

salt/graphite/files/requirements.txt

@@ -8,4 +8,5 @@ gunicorn
 pytz
 pyparsing
 whisper
+carbon==0.9.12
 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