Allow the grains to set our workers and celery count (#87)

Ops has optimized on the amount of workers we should have based upon our orca .sls. We should follow this pattern and allow this to updated based upon what ops likes

Where grain is set:
https://github.com/lyft/salt/blob/1308c64f5ab9ae5f735f6e404e6e3aa16a87ab37/salt/grains/core.py#L90-L140

@lyft/command-center @mistercrunch @amalakar @betodealmeida

ops/config/pillar/superset.sls

@@ -6,10 +6,10 @@
   }%}
 {% else %}
   {% set conf = {
-    'web_workers': 8,
-    'celery_workers': 32,
+    'web_workers': grains.num_cpus,
+    'celery_workers': grains.num_cpus * 4,
     'timeout_sec': 120,
-  }%}
+  } %}
 {% endif %}
 
 python_executable: python3.6